Sunday, June 24, 2012

GCNP boundary: A Revised map from NPS

After over two years of work and intra-agency discussion, the NPS Land Resources Division has made available files that represent its latest thinking (see at end for my comment about accuracy) about where NPS boundaries lie that affect Grand Canyon National Park, i.e., for the Park and Lake Mead NRA. 

Here is how I went about getting a look at the maps. I want to acknowledge the help that Roger Johnson of LRD and his staff gave me. 
The website that NPS stores its map data on is
I could not use Safari to get there, but Firefox works, as well as Explorer and Chrome.

On the IRMA Portal "Welcome" page, click on "Featured Content" near the top right of the page.  Then click on "NPS Park Boundaries" for the GIS data set to obtain boundaries for the units that have gone through the Lands Resources Division (LRD) digital data conversion process. 
On the page that comes up, click on "Search" to get drop downs: Select "Data Store" and "Advanced". 
On the Data Store Search page, under "Search Fields" (you may have to click on "Expand Panel" to see them)  do the first drop down to select "Title". The next field should say "containing". In the third field, type "tract and boundary".  Then go to the Units and click on the down button, and where it says "Select a unit…" type "GRC" and enter the Park. Since all parks whose boundaries have been approved for release by LRD will also have tract data available for download, you can search through the list for other units, like LAKE for LMNRA. 
Press "search". You should get the "display citation" page  for the Park. Click on the middle of the line, to get the data page.

In the middle of a line near the top of that page, "View Source XML" stands out darkly. Pressing this will bring up a hard-to-read description of data quality, etc. This is the metadata (I will write about this in an upcoming post). Then halfway down the page, under "Holdings" is the tract data file. It is zipped for each Park unit and named {alpha code}, e.g.
Click on "Download" to get the zipped file. For some reason, I had to use Windows to unzip the file, an essential step. Unzipped, you get:
The eight files with shx, shp, dbf,  prj are the crucial ones for making a map. So once unzipped, I had to put them in a group, and zip them back up again. Then I could use ARCgis Explorer to do a new map. That is a whole other topic.

Of more pertinence is a caution: The NPS map has problems. I will discuss this issue in a subsequent post, but for now just be careful about what map you rely on. As I have previously written, available maps like Forest Service, BLM, National Geographic, etc., have made choices that differ from the official map and from each other. No doubt the biggest problem has to do with pieces of the Navajo and Hualapai Reservations. 

No comments:

Post a Comment