Major progress to report. One version is the generic unit map, the
other (messier) version is the more finely divided map.
other (messier) version is the more finely divided map.
Friday, April 30, 2010
Friday, April 23, 2010
State of the Map: Clark County, Nevada (2)
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.
State of the Map: Clark County, Nevada
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!
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!
Tuesday, April 20, 2010
State of the Clark County (Nevada) Map
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.
Friday, April 16, 2010
Editor Tracking Tool in ArcGIS.
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?
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?
Tuesday, March 2, 2010
Slopeshade v. Hillshade for bedrock contact mapping
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:
Happy mapping!
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