Nevada Digital Dirt

This blog has run its course.

2010-09-01T15:30:00.000-07:00

The Nevada Digital Dirt Mapping ~~Project~~ Experiment is over. Our mapping team demonstrated that it is feasible to develop a 1:150,000 scale surficial geologic map of 20,000 square kilometers in 18 months. Our approach represents a valid model for collaboratively developing geologic maps of large areas in short periods of time.

Thank you for your interest in our endeavor.

Wow. I may just get my life back soon.

2010-06-29T18:41:00.001-07:00

Maybe some real sleep too. Over-dedication is over-rated. Now I know for sure.

Posted via email from Fresh Geologic Froth

So, this happened.

2010-06-29T17:14:00.001-07:00

A big day for the DirtMap...it is complete enough to submit. In
celebration, I urged a colleague at a similar institution to help me
go live with the map.

You can temporarily view it here:

http://services.azgs.az.gov/OnlineMaps/demos/nvClarkCounty.html

Now, to finish that darn report by 3 PM tomorrow.

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1000s of miles of lines...

2010-06-28T16:28:00.001-07:00

The colorful map shows the compiled linework that we started with.
Much was extensively modified to better illustrate the array of
surficial geologic deposits. The redline map shows the final
(preliminary) result of the modification and the addition of many,
many, many additional lines. Note that we simplified the bedrock.

Thus, some of the line density decreased as well.

See the full gallery on posterous

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Three representations of the Clark County DirtMap

2010-06-28T16:22:00.001-07:00

Illustration of progressive levels of generalization...from most
detailed, to genetic category, to fundamental category.

See the full gallery on posterous

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Holy freaking crap, it's a freaking map!

2010-06-25T16:43:00.001-07:00

See a mistake? Keep it to yourself. Our team collectively put a few 1000 hours into this product. It is the only complete map of the surficial geology of Clark County, Nevada that you are going to find.

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The Dirt Map Correlation Chart....Revised

2010-06-25T11:15:00.001-07:00

This is getting closer. Have had to impose a moratorium on additional mapping at 3 PM tomorrow. today. Working on the report.

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The Dirt Map Correlation Chart....

2010-06-24T17:43:00.001-07:00

This is getting close. Have had to impose a moratorium on additional mapping at 3 PM tomorrow. Working on the report.

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Clark County Mega-map: One week to go...

2010-06-22T16:58:00.001-07:00

There are no perfect maps. Trust me, there truly aren't.

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Nevada Digital Dirt Presentation

2010-06-07T20:08:00.001-07:00

The_Nevada_Digital_Dirt_Mapping_Project.pdf (4007 KB)
View this on posterous

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State of the Clark County map, June 4, 2010

2010-06-04T17:21:00.001-07:00

Bear with me here. This one clearly demonstrates the progress to date by showing all of the units we have divided. Less than a month to go...oh right, with 7 days of field camp in the middle. Wish us luck.

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State of the Clark County map, June 1, 2010

2010-06-01T13:34:00.001-07:00

The map just keeps getting better. Tying up some loose ends, dealing differently with the Muddy Creek Formation, addressing some reviewer concerns based on a much older version, etc. Presented this map at the Digital Mapping Techniques Workshop in Sacramento a couple of weeks ago. Reaction to talk and map indicates that this map was made in record time for a record bargain.

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State of the Clark County map, May 21, 2010

2010-05-21T17:22:00.001-07:00

Still churning along.

See the full gallery on posterous

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The Clark County 'Dirt' Map: Only 16.5 months in the making....1.5 months to go.

2010-05-12T13:06:00.001-07:00

Despite combining this monsterous map with just a few other mapping 'efforts' this thing may actually get finished!

Note that this is the generalized version. Still working on the detailed version. Will be describing this project and the value of 'supervised Crowd-sourcing for rapid geologic map development' at the Digital Mapping Techniques workshop in Sacramento next Monday.

http://www.conservation.ca.gov/cgs/News/Pages/DMT2010.aspx

Nevada Digital Dirt Mapping Project Team members:

Rachel Wearne

Larry Garside

Alan Ramelli

Joanna Redwine

Ronna Bowers

Jason Man

Michell Rose

Luis Rodriguez

Molly Hunsaker

Dan Kozar

Rohit Patil

Justin Skord

Jim Trexler

Pat Cashman

Jill Heaton.

Yes...there are some problem areas. Relax. We know about them.

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State of the Map: Clark County, NV

2010-05-08T10:32:00.001-07:00

Again, significant progress to report. Thanks to Dirt Mapping team
co-leader Heather Green for keeping things in line while I panic about
too many other projects.

See the full gallery on posterous

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Clark County Seven Ways

2010-05-05T11:49:00.001-07:00

An example of the array of base imagery that we are using to build the
surficial geologic map of the county. Some look far better (and some
far worse) at larger scale.

See the full gallery on posterous

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State of the Map: Clark County

2010-04-30T17:44:00.001-07:00

Major progress to report. One version is the generic unit map, the
other (messier) version is the more finely divided map.

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State of the Map: Clark County Lines

2010-04-30T17:34:00.000-07:00

State of the Map: Clark County, Nevada (2)

2010-04-23T15:58:00.003-07:00

Immediately following the previous post, I got this image from the
team's co-leader. This one portends the diversity in the final map
that we have planned.

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State of the Map: Clark County, Nevada

2010-04-23T15:58:00.001-07:00

The clean version indicates the huge progress that we have made in
developing the generalized map. The 'messy' version portends the
variety of alluvial fan deposit (mainly) that we will soon be
beginning to methodically attribute and carve-out (where
necessary) to create the finished map.
Hooray for the Nevada Digital Dirt Mapping Team!

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State of the Clark County (Nevada) Map

2010-04-20T10:33:00.001-07:00

Huge progress in last two weeks. Leveraging the skills of multiple
users in ArcSDE...would be dead without it. A viable example of
'supervised' crowd-sourcing of geologic and gis expertise.

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Editor Tracking Tool in ArcGIS.

2010-04-16T15:14:00.001-07:00

Presently, I am trying to manage 9 mappers working simultaneously on the Clark County surficial mapping project...the number may swell to about 12 or 15 in the next week or so. This effort is being made possible by using ArcSDE...there is really no other way to do such a thing efficiently...more on that later.
Recently, we discovered an editor tracking tool that can be installed that provides records of who edited what and when. We found it quite late in the game, but now that we have had it for about 3 weeks, it provides a useful and promising perspective on the progress with the map. Each line that is touched by an individual and edited in some way (no matter how small) becomes tagged with that person's ID. Looking at the map symbolized by mappers is interesting, shows progress, and also...well...lets you hone in on potential trouble spots. Also, the fact that if an editor touches a very long line by fixing only a small segment helps motivate the individual to investigate the entirety of the line. Sweet!
The tracking tool can be downloaded from ESRI at: http://arcscripts.esri.com/details.asp?dbid=15694
Here is an example that shows the tool's results as well as some serious progress on this huge, huge, huge map. Did I mention that the map is huge?

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Slopeshade v. Hillshade for bedrock contact mapping

2010-03-02T20:53:00.001-08:00

The Digital Dirt Map of Clark County, Nevada is proceeding with a team of 13 now. The goal is to complete the map by May 1 (!), so the team may grow by a couple more members soon. One of the key issues that we are currently grappling with is the refinement of the bedrock-alluvium contact in areas where it is poorly expressed by existing sources. For the most part this includes areas previously mapped at only 1:250,000 scale. Areas previously mapped at smaller scales (1:100,000 and 1:24,000) are far less problematic.

Accurately mapping this contact for a final scale of 1:150,000 for our compilation requires some basic approaches. For one thing, I have been actively training a capable team composed primarily of geography and geology students, so the learning curve isn't too steep. To discern the primary contact, we have multiple base sources at our disposal (e.g., ASTER, NAIP, ETM) as well as a nice hillshade image of the county based on the 10-m DEM data. This particular base image alone allows for a massive improvement in some of the preexisting geologic linework on the basis of distinguishing predominantly steeply sloping and irregular bedrock outcrops from less steep and generally smoother alluvial, aeolian, and playa deposits. However, applying a manipulative trick that maximizes the value of LiDAR imagery for topographic visualization, it is possible to leverage even the 10-m DEM for better results.

The approach is to develop a slopeshade map. In the case of a slopeshade map, all steep slopes are shaded and all gentle slopes are illuminated....no matter what their aspect. It is essentially an isoshade representation where the sun is shining from all angles at once.

Here are some examples with the 10-m Clark County data, starting with the hillshade:

Looks nice, no? This is a very pleasing way to present the county in cartographic form.

Here is the slopshade version of the same data:

It is quite stark in comparison, but it conveys the topography in a very useful way. Consider the smaller scale versions of the Arrow Canyon area presented below:

The Hillshade version:

The slopeshade version:

Note how different these two images are. In the case of the slopeshade, no topography is masked by shadow. Every slope is rendered in the same way no matter which direction it faces. In this rendition the primary contact between rock and non-rock is quite clear.

For more examples and an explanation of how easy it is to derive this type of image, check the following links:

http://geofroth.posterous.com/useful-new-lidar-love-tips

http://geofroth.posterous.com/more-lidardifferent-river

Happy mapping!

Posted via email from Fresh Geologic Froth

Nevada Digital Dirt Team undergoes major expansion

2010-02-22T08:11:00.000-08:00

Over the past several weeks, I have initiated a major expansion of the Dirt Mapping Team. Completing such a large map by the beginning of May (!) is a mammoth undertaking. As the previous post indicates, we have made significant progress, but it has become clear that the active mapping team was too small (essentially, two of us). The increase in membership has been greatly facilitated through direct cooperation with the affiliated ecosystem mapping and GIS team from the UNR G-lab, and from some 'hand-picked' UNR geology students and profs with skills in mapping and GIS.

Thus, we now have up to 11 contributors performing at various levels and time commitments. Currently, our main tasks are improving existing linework from compiled map sources and dealing with mapped units that are below our minimum map unit threshold. The first step in the linework improvement phase is modification/reshaping of the contact between bedrock units and surficial units. This turns out to be the easiest step for new 'recruits' to understand and master. The process is greatly enhanced by including multiple imagery types and shaded relief models as base layers which allow for different, yet complementary perspectives on the landscape. Also, running Google Earth in an adjacent monitor is also quite handy. Oh right...the G-Lab also got some sweet new Wacom digitizing tablets as well.

We are using versioned geodatabases in ArcSDE. to allow for independent and concurrent editing among all of us. This is the best scenario for a multi-mapper effort. Thanks to Abbey for managing the whole affair.

The ideal trajectory of mapping participation is as follows:

1. Contact between bedrock and surficial deposits (currently underway)

2. Contact between different master classes of surficial deposits (e.g., alluvial fans from playas, etc.)

3. Contact within master classes of surficial deposits (e.g., alluvial fan deposits of different ages)

Progression through these steps will depend in large part on performance and time available to map. Most team members have been assigned a 15' by 15' (minutes of lat and long) cell in which to work on the bedrock contact. They are tracking their time. Every cell will be evaluated for consistency and accuracy by the team leaders.

To date, I have spent several hours providing tutorials about the most efficient ways to carry out the bedrock / non-bedrock contact and will spend some more time this week to make sure everyone is up to speed. Also, several times in the last few months I have been able to provide some instuction / explanation in the field about the nature of the deposits we are mapping.

Generalized map of surficial and bedrock units as of February 2010

2010-02-08T13:10:00.000-08:00

The Clark County dirt mapping team will soon expand from 4 to 7 or 8 as we approach a key deadline. The morass of linework remains a major issue, but we are slowly refining it into a clean data set. Here, I thought I would take a step back and evaluate the map on a more fundamental level...that of key mappable unit types. Much of this map reflects the original data sources that we are refining, but it provides a very nice overview of the distribution of the key map unit types in the county. The deposits are not divided by age in this rendition...just process / deposit type.

As the full team begins to take on the county en masse, I will post updates of this particular representation as it evolves.

If you are one of the few that view my Geologic Frothings Blog. Please note that the newest manifestation resides at http://geofroth.org.

2010-01-21T10:28:00.001-08:00

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Minimum mappable unit blues

2009-12-17T16:58:00.001-08:00

I have a tendency to map in great detail...even when it is unwarranted or relates to a largely inconsequential stratigraphic situation. This problem is proportional to the quality of the base imagery that I have or the intrigue-level of the units in the field. However, in my quest to lead the effort to develop a surficial geologic map 10,000 sq. km. of dirt in Clark County in a compressed time frame, I am learning that it is ok not to sweat the details, as long as you explain what comprises the mapped units. One thing that we have learned is that it is essential to develop an agreed-upon minimum map unit area (mmu). That is, the smallest polygon that is mappable at the chosen scale.

As far as I can tell, geologists are not very keen on the mmu, whereas the dirt mappers in the NRCS have codified the concept in their considerably more standardized procedure.

We have adopted a visual approach that is based on the basic legibility of a polygon at a specific scale, and have concluded that 10 hectares is a good minimum value to start with. Ten hectares covers 100,000 square meters...or a square that is approximately 316 meters on a side. Sounds kinda big, looks quite big in the field, and certainly looks mappable at 1:24,000. However, if you zoom out to 1:100,000, the story changes.

The map below shows a random area in the county at 1:24,000. A selection of polygons is labeled with respect to size in hectares.

Sure, those all look totally mappable, right? Well, not so much. Check out the area when outlined in a 100k map:

(note: larger images viewable at:
http://geofroth.posterous.com/minimum-mappable-unit-blues)

Now the story is different. Not only are the small polygons bordering on illegible, the scale of the task of mapping such small polys consistently in a reasonable amount of time is impractical without a huge expenditure of time.

There are some side effects of eliminating units below a certain size threshold. One is data loss. That will be handled by preserving the small polys as points. Thus their locations will be stored as will their attributes. This solution can also facilitate the mapping process by flagging those polys that need to be absorbed into larger, surrounding or adjacent ones. One other problem is the case of high-standing inselbergs. Some of these are very tiny, but protrude several meters above the surrounding surficial deposits. Thus, their omission is particularly notable when in the field. For example, in the photo below, the fairly conspicuous cluster of red sandstone inselbergs has an areal extent of approximately 10 ha.

Not mapping such a feature may seem like a total affront to the sensibility of a geologist, but there will be a point there in the dataset that indicates an awareness of the feature's existence.

Generalized Parent Material Map Progress

2009-10-28T16:09:00.000-07:00

We recently generalized the existing bedrock geologic data for Clark County into 19 general lithologic categories. Our goal is to provide clear context for evaluating parent rock materials for the array of surficial deposits that we are compiling and mapping in more detail.

The units have been preliminarily divided into the following 19 categories (2 not yet used on the map):

Sedimentary Rocks (S)

Carbonates (Sc)
Limestone (Scl)
Dolomite (Scd)
Interbedded limestone and dolomite (Scld)

Siliciclastic sedimentary rocks (Ss)
Mudrock and shale (Sssh) (not yet used)
Chert and argillite (Ssc) (not yet used)
Sandstone and coarser (Ssss)
Interbedded shale and sandstone (Ssshss)

Interbedded carbonates and siliciclastic sedimentary rocks (Scs)

Igneous Rocks (I) Plutonic (p) Volcanic (v)

Felsic igneous

Intrusive (granite) (Ipf)
Extrusive (rhyolite and tuff) (Ivf)

Intermediate igneous
Intrusive (diorite) (Ipi)
Extrusive (andesite) (Ivi)

Mafic igneous
Intrusive (gabbro) (Imi)
Extrusive (basalt) (Ivi)

Mixed volcanic rocks (Ivx)

Metamorphic (M)

High grade (crystalline rocks) (Mh)
Low grade (phyllite, argillite, quartzite) (Ml)

It may be that this is more detail than is warranted...or maybe it is not quite enough...opinions will vary. The data are structured in such a way that ratcheting the detail up or down is not complicated. The goal is to work with the existing data in a consistent way across the study area.

Also, note that this project does not involve remapping any bedrock units other than where the boundaries with the Q deposits can be improved.

Correlating units from many maps

2009-09-15T11:57:00.000-07:00

We reviewed the nomenclature for the existing maps that cover Clark County and correlated those units to the newly-developed Clark County nomenclature based on deposit type, what materials it is composed of, and any age constraints. In cases where the units do not correlate well, we simply added additional units to the Clark County nomenclature to accommodate the existing map’s nomenclature.

The following maps were compiled:
Las Vegas 100k: usgs sim 05-2814
Lake Mead 100k: usgs ofr 07-1010
Mesquite Lake 100k: usgs ofr 06-1035
Ludington, unpublished data
Death Valley ground-water model area, 250k: usgs mf 2381
Colorado, White River, and Death Valley groundwater flow systems, 250k: nbmg m150

This list of units with brief descriptions is the current Clark County nomenclature.

The following correlation diagrams are split by deposit type and show how all the compiled maps correlate to each other and to the new Clark County nomenclature.

Making one map from six: Fun with ArcGIS!

2009-09-15T11:52:00.000-07:00

It took a great deal of experimentation to get the final data sets merged and ready to work with. Below are the steps we used to do this.

Downloaded original data.

Checked projection. Is it defined? If not, define it (define projection tool).

Several data sets were in UTM NAD 27. Our final map will be in UTM NAD 83. So, re-projected NAD 27 data sets to NAD 83 (project tool).

Where data extends beyond the county, we clipped it (clip tool). Where data sets overlap, we chose to keep the larger-scale data and clipped the smaller-scale data to it.

Imported the data sets into an sde, creating line and poly feature classes for each map.

Attributes: To each line feature class, we added attribute fields named CC_ltype, orig_OID, orig_ltype, and source. To each polygon feature class, we added attribute fields named CC_surf, CC_rox, orig_OID, orig_unit, and source. Orig_OID, orig_ltype, and orig_unit were populated from the original data as a way to preserve and refer to the original data. CC_surf was populated based on unit correlations. All attribute fields besides the ones listed above were deleted.

All of the line feature classes were then merged into one line feature class, and all polygon feature classes into one polygon feature class. The merge tool is pretty straight forward, but behaves in ways I can’t claim to fully understand. Even though all the data sets had the same attribute fields, the merge tool appears to be picky as to the order in which you add data sets that you want to merge. For example, I was unable to merge all of the data sets at one time. I had to merge smaller groups of data sets and then merge the merged groups. I’m not sure why, but it worked.

We are now ready to start adding our own lines and modifying the existing data if needed!

First glimpse of the unified surficial geologic map of Clark County

2009-08-03T17:33:00.000-07:00

This map represents the results of our attempt to unify the surficial geology and geomorphology of Clark County as expressed in available digital data sources spanning most of the county. Much work remains to be done to fully unify the various sources, but this is a big step.

Soon we will develop a 'postable' figure showing our interpretations of the published data that were unified, thus explaining the colors on the map. In the example above, the bedrock is not shown (note that the dark green is vegetation indicated on the base map).

Realizing Full Coverage of the County at 100-150 k

2009-08-01T12:30:00.000-07:00

A recent increase in dirt mapper activityhas resulted in a collective dataset covering ~75% of the county. These data from USGS and NBMG sources are presently being unified into a single classification scheme based on common process, material, and geochronologic characteristics. We will soon post the unifying scheme for comments.

We also are pursuing a couple of leads that include mapping of the remaining part of the county. We currently have our hands on a hard copy of a generalized bedrock map of Southern Clark County that we know will suit our needs well.

Geochronology Catalog in Google Earth

2009-07-08T14:33:00.001-07:00

The Nevada Digital Dirt team has initiated a compilation of published geochronological data for Quaternary deposits in Clark County, NV. We are using the Google Spreadsheet Mapper tool to depict the data. Once we reach critical mass on the number of points from the available published sources, we will share the kml file and request suggestions for correcting any positioning or misattribution. So far, everything is under control with respect to the latter, but the former may need some work.

As you can see, it is a very intuitive way to depict and explore the data. Imagine if it were done for all the rock and dirt dates in the western US...

Update: Sorry for the Hiatus! We are working.

2009-07-04T15:11:00.001-07:00

Other projects have engulfed my time for the last several months, but significant 'background' progress has been made in developing a unified nomenclature for the surficial deposits of Clark County. We have been working up some diagrams and derivative maps from the existing data which we will post in the next couple of weeks. Sorry for the delay.

Initial approach to evaluating available digital geo data

2009-02-19T16:14:00.000-08:00

A previous post pointed out that some existing mapping of surficial deposits at 100k was inadequately detailed for the purposes of this project. We quickly made that assessment by draping the linework on imagery viewed in Google Earth and in ArcGIS. It is very likely that had the various geologists who developed this mapping over the years had such easy access to high-resolution imagery and GIS, then the mapping would be considerably less inadequate!

The example above shows the lines from the Lake Mead 100k map (USGS open-file data) in Google Earth. It works very well when zoomed into specific areas (down to 1:6000, for example), but the overall heterogeneity of the base imagery is a bit distracting. From this image (and the next) you can see that the detail in the bedrock is somewhat to considerably greater than that in the 'dirt'.

The image below is from ArcGIS and the lines from the Lake Mead 100k sheet are overlain on NAIP imagery. This imagery is also great when zoomed in and is homogeneous with respect to overall color balance, tone, etc. It is also from a much smaller window of time.

Our team has recently set up an image service at the UNR Geospatial Lab (Geography Dept.) that allows each investigator on the project to access the same high-resolution imagery remotely. Thus, we do not have multiple copies of giant .tiff files on all of our various computers. This is extremely helpful for collaboration and ensuring that everyone has equal access to the base imagery.

Surficial Geology Detail Comparison: Ivanpah Valley

2009-02-13T16:11:00.000-08:00

There are two data sets of surficial geologic mapping that cover the Clark County part of Ivanpah Valley. The first one is from an NBMG map that I made. It is far too detailed to serve as a basis for mapping the entire county:

The same area from the 100k Mesquite Lake map shows considerably less detail, but relies on composite / combined units to account for this in most cases:

The Mesquite Lake snip above is from a map in which Ivanpah Valley is only a moderately small part. The map I developed (with help) was focused entirely on Ivanpah. As mentioned in a previous post, we are leaning toward some point between these two renditions. The NBMG map (published at 50k but mapped at ~12k) is excessively detailed and the USGS 100k map is a bit too general for what we would like to develop with the ND2MP. For example, we hope to map fewer composite units.

We suspect that we will ultimately end up closer to the USGS characterization of Ivanpah than to the NBMG characterization....not sure yet. We are actively applying generalization routines of various sorts to the NBMG data set. I will post a few examples next week.

An example of coarse detail on 100k map

2009-02-13T15:28:00.000-08:00

As promised, and with no offense intended, here is an example of an area from an existing 100k geology dataset of Clark County that is clearly inadequately detailed from my perspective as a surficial mapper:
I made the contacts red to be obvious. Most of the tonal variations that you see in the image represent distinct surficial piedmont units. Many that have been lumped together are quite large and also span a huge range of time as far as surficial deposits go. Also it is not clear why some large active washes were mapped individually and other, larger ones weren't. This approach to mapping is covered in the unit descriptions from this map for the most part, but for our purposes, additional mapping is certainly required.

Digital Dirt Map Compilation Chronicles, Part 1 of MANY

2009-02-13T12:58:00.000-08:00

To date, the ND2MP 'staff' has been compiling all of the existing, digital renditions of the geology of Clark County, Nevada. Luckily, the USGS has been compiling and developing 100k maps across the county and has, thus, done a fair amount of work for us already. What follows is a descriptive update of what we have been doing. Stay tuned for some graphic examples.

We have started to evaluate the relative worth of the various map data that we have in hand, and have gained some important insights.

First off, kudos to those authors who have pored over existing maps of a range of scales to develop their compilations (e.g., USGS versions of the Las Vegas 100k, Lake Mead 100k sheets). We are keenly aware of the huge amount of work that went into that process, and we are also aware that it involved new mapping in some areas. Even more kudos to those authors who generated large amounts of original mapping at similar scales (e.g. USGS version of the Mesquite Lake 100k). That was obviously a huge effort.

Given this, however, there are several facts about these maps that bear directly on our efforts. For example, there is a high degree of variability in the level of detail in the compilation maps. This fact is pointed out by the authors, so this comes as no shock to anyone. However, as we develop the surficial geologic map of the entire County, we are interested in developing a dataset that has a consistent level of detail across the entire area. This will be a large task. It will involve mainly enhancing the detail in existing compilations, but will also involve some generalization of overly detailed areas.

The latter point applies, for example, to the Ivanpah Valley area, where House et al., mapped in detail and Schmidt and McMackin mapped more generally. What we want for the ND2MP is somewhere in between those extremes, so we are experimenting with some automated generalization routines with the House et al. data and comparing the results to the Schmidt and McMackin mapping. I will post some examples when they are ready. Areas where the existing compilations are simply too general or appear somewhat arbitrary in detail will require significant amounts of new mapping as part of this project.

As for generalizing existing overly detailed maps, we are going to establish a minimum map unit criterion between 5 and 10 hectares. This refers to the areal extent below which we will not show a polygon. With respect to existing compilations, we plan to express polygons below the threshold as point-features in the database. We are also experimenting with ways to efficiently eliminate parts of polygons that are less than 30-50 meters wide. This issue arises mainly in the area of single-thread active washes. Ideally, we can collapse the narrow polys to centerlines that retain the atttribute when needed. This is sort of an 'annealing' function that digital cartographers are experimenting with, but we can't find any explicit add-in for doing it in ArcGIS except when it involves the distance between two polygons and not parts of the same polygon (doesn't create the line we want, however). When we progress in these areas, I will post examples to this blog.

Another arguably more important issue is that the existing compilations use different nomenclature for the surficial deposits. Given that several of these maps probably had overlapping compilation periods, are contiguous, and are from the same agency this is a bit surprising. However, I too have some pretty schizophrenic labeling schemes on my own maps and NBMG has no formal standard, so I can relate somewhat. In any case, for a county wide depiction of surficial geology that we want to ultimately apply statewide, it is absolutely necessary that we develop a consistent, flexible, and understandable framework. Each of the existing compilations provide some good and well-reasoned examples. We will begin with them and either choose the one we think is the best, or possibly confuse the issue more by developing a framework that we think is better. In any case, we will develop a rubric that explains how the various schemes relate. Currently, we are leaning toward a composite of the Las Vegas 100k approach with the Mesquite Lake 100k approach.

Stay tuned for an upcoming post that provides an opportunity to view and comment on our proposed scheme and its rationale. I will also prepare some examples of areas in need of generalization or more detailed mapping to support my statements above.

Ecosystem Indicators Project Research Objectives

2009-02-03T12:16:00.000-08:00

ND2MP is supported in part by the Ecosystem Indicators (EIP), funded by the Clark County Multiple Species Habitat Conservation Program (MSHCP). The EIP has three main research objectives, ND2MP being a portion of one of those objectives. Objective one is to establish a robust GIS-based characterization of the geomorphology and surficial geology of Clark County, Nevada (i.e. ND2MP). Although the term ‘habitat’ is often used loosely as equivalent to ‘native vegetation’, this is not always the case. Nonetheless, scientist and managers continue to use vegetation as a means for defining habitat. Geologic materials provide an alternative and at times more appropriate means of defining species habitat and extent of vegetation communities, especially in arid environments (Miller and Franklin 2002, Heaton et al. 2006).

Objective two is to map the ecosystems in Clark County. The MSHCP uses an ecosystem-based approach to conservation planning and management for plant and animal species. We will update and refine the current vegetation based ecosystem model for Clark County. This includes the identification and spatial modeling of various NatureServe based Ecological Systems, Alliances and possible Associations. Our goal is to capture important ecosystems that include such broadly defined vegetation classes as blackbrush, sagebrush, pinion-juniper, saltbrush, creosote bush, Joshua Trees, etc. Additionally, we will for the first time develop spatial models for non-vegetation based MSHCP ecosystems such as dunes and dry lakes.

Objective three is to develop an enhanced vegetation based ecosystem classification model in three pilot areas using more intensive sampling, advanced spatial statistical methods and object-oriented classification and the newly developed geomorphology and surfical geology datasets. Current pilot areas under consideration include Piute-Eldorado Valleys, Ivanpah Valley, Gold-Butte and Kyle Canyon area across to the Sheep Range.

Introduction and Explanation

2009-01-05T06:07:00.000-08:00

Welcome to the blog of the Nevada Digital Dirt Mapping Project (Phase 1).

The Nevada Digital Dirt Mapping Project (ND2MP) is an initiative to collaboratively compile a surficial geologic and geomorphic map of Nevada at approximately 1:100k. Phase one of this project spans the entirety of Clark County, Nevada, and began in November 2008. It is to be complete by May 2010. Actual field and office work will commence in January 2008. We hope to ultimately extend the mapping and the related conceptual framework to the entire state of Nevada.

The project's focus on surficial geology and geomorphology reflects interest of currently available sources of funds. It will also be easier to deal with than the bedrock. If fully realized, the map data set will be an essential resource for geoscientists and possibly a model for similar projects in adjacent states or regions.

As it progresses, the mapping will be made available online. It will be accompanied by sets of geotagged photos, high-precision GPS data points, and a GIS database of published geochronological data, among other things. The goal of this blog is to chronicle the development of the data set and, more importantly, to actively engage the relevant members of the geological community in discussing, critiquing, and reviewing the development of the map.

Our goal with Phase 1 of ND2MP is to develop a fully digital surficial geologic map of Clark County by compiling all existing digital geologic data sets that adequately portray surficial deposits and generate new mapping in areas where the surficial geologic detail is lacking. We will develop a geologic nomenclature that is commensurate with existing, well established frameworks established in the most detailed published maps. Any changes the we propose will be offered to the relevant members of the geologic community for comment during (not after) initial compilation of the map.

The final point above is key. This project is being initiated as an experiment in online scientific collaboration. We are keenly aware that many geologists have published maps and have carried out detailed research projects in Nevada, particularly Clark County. Our goal is to maintain an open and collaborative mapping effort that transcends simple compilation of existing mapping. In other words, we are completely open to direct input from all interested and qualified scientists who have mapped in the area. This may include, for example, guidance in modifying or generalizing published mapping for the compilation, inclusion of relevant, unpublished data, revision of published mapping, etc. There are many possible examples.

This blog will soon have a companion website or data portal that will serve up the map data for others to review. We hope to develop a streamlined method for providing data in a format that can be viewed on multiple platforms. Give us some time to figure that part out...