GSDA:Using GIS Data Depot to Obtain DEM, DRG, and DOQ Data
GIS Data Depot is a good source for data used by GIS and WMS. You will find a large selection of DEMs, DRG images, and DOQs.
- NOTE: Only the DEM data (in SDTS format) can be downloaded for free. Or any downloads with the (green - normal) icon.
Before you can pick what data to download, you must specify which country, state, and county you need data for. For the United States, the USGS Geographic Names Information System (GNIS) can help you determine which county a particular feature (e.g., stream, city) is located in. To learn how to use GNIS, click here. The GNIS will also tell you what USGS quadrangle the feature is located in since individual DEMs and DRGs are named after their respective quadrangle.
- Go to www.gisdatadepot.com.
- Click the Download GIS Data button.
- Click the state of your choice on the US map. A new window will pop open with all counties in that state with available data.
- Click on the desired county name from the list of county links. All information accessible will be listed.
- TRIAL Walkthrough (optional): To locate Deer Creek Reservoir on a trial browse-through select Utah state and Wasatch county.
- Choose the link below which corresponds to the type of data you want.
Obtaining DEM Data
You can download 7.5' quadrangle DEMs (1:24,000 scale or "24K") from GIS Data Depot for free in SDTS format. Other formats may be available at a small fee. If you already know the quad name of the DEM you want continue with the steps below. If not then use the USGS Map Locator to determine the quadrangle map name (see the tip on Using the USGS Map Locator). You may also use the USGS Geographic Names Information System (GNIS) to find the correct quad (see the tip on Using the USGS GNIS).
- Click on the Digital Elevation Models (DEM) - 24K link.
- Locate the link(s) for the DEM(s) you need. TRIAL WT (cont'd): Deer Creek Reservoir is known to be in the Aspen Grove, and Charleston quads.
- Click on the "free" Normal Download icon . NOTE: You will be required to create an account in order to download ANY data. Money must be paid to your account before they will allow you to download any purchasable data. You will not be charged anything for normal downloads.
- Follow the given instructions to download the file. TRIAL WT (cont'd): Aspen Grove 30 meter filename: 1694326.DEM.SDTS.TAR.GZ Charleston 30 meter filename: 1635940.DEM.SDTS.TAR.GZ NOTE: Please be sure to also download and view the DEM's accompanying text file for this file contains the DEM metadata. Aspen Grove text filename: 1694326.DEM.SDTS.TAR.TXT Charleston text filename: 1635940.DEM.SDTS.TAR.TXT
- Decompress the file. Click here for help with decompressing data files. There will be 20 files, most of which have a *.ddf extension. You have now obtained the DEM data.
Obtaining DRG Data
Usually GIS Data Depot has the option of 24K, 100K, and 250K scale DRGs. DRGs are named after their corresponding quadrangle maps. If you need to figure out which quads you need, you can use the USGS Geographic Names Information System (GNIS), (see the tip on Using the USGS GNIS). Another useful tool is the USGS Map Locator, (see the tip on Using the USGS Map Locator).
- Click on the Digital Raster Graphics (DRG) - 24K link to obtain a 1:24,000 scale DRG. There could be other scale DRGs available.
- Find which DRG you need.
TRIAL WT (cont'd): Deer Creek Reservoir is known to be in the Aspen Grove, and Charleston quads.
- Click on the Premium Download button next to it.
NOTE: You must be logged into your GeoCommunity account in order to download. If you have sufficient download bytes remaining in your account you can download the DRGs. If you do not you will have to purchase more.
- Follow the instructions for downloading the file.
- Once downloaded, decompress the file.
Click here for data file decompression help. You have successfully obtained the DRG, which can now be imported into WMS.
You also can view the TIFF image itself in most any graphics program such as Paint Shop Pro. The image is fairly large and will not look clear when you are zoomed out to the full extent of the image. You can zoom in to get a clearer view and more detail. This is why it is important to select the correct scale of DRG depending on how large your watershed is. Try zooming into a portion of the image such as Doylestown on the east side of the image (see below).
Obtaining DOQ Data
GIS Data Depot has limited DOQs available. There might not be any to download for your specific location at present, but they are working toward having all states covered. To locate your DOQs you will need to know the state and county it's in. Use the USGS Geographic Names Information System (GNIS) to determine where it resides, (see the tip on Using the USGS GNIS). The USGS Map Locator might also be helpful, (see the tip on Using the USGS Map Locator). Like DRGs, DOQs are not free at GIS Data Depot.
- Choose the Digital Orthophotos (DOQ / DOQQ) - 1 Meter link.
- Locate the DOQs you need and click on the Premium Download button next to it.
- Follow the downloading instructions. This file is in the MrSID (*.sid) format which stands for "Multi-resolution Seamless Image Database." WMS cannot directly read images in the MrSID format. However, an application is available that will save the MrSID image as a TIFF image, which can then be opened in WMS. The name of this free application is MrSID GeoViewer and can be downloaded from LizardTech.com