The GISuser's Guide to locating and downloading Free USGS data

So, you need to work with USGS data. Perhaps you need DRGs, maybe some DEMs, or maybe even some DOQQs. Before you begin the search, make sure your familiar with some of the pieces of information we’ve provided below. Which quads do I need? How can I translate and/or view the data? Where can I download the data? Read on for some answers to these questions and more.

Are you searching for free, downloadable GIS data? A number of colleges, government agencies, libraries, and other publicly funded entities have the data you require and its free to download. Data products include USGS DRG, DLG, DOQ, and DEM data, as well as many other data themes (availability varies by State).

Did you know… many of these resources also have USGS DEM data available for free download which may come as a surprise to you as the USGS has indicated that these data are now only available from select commercial data providers where user registration may be required.

NOTE: The 24k SDTS DEM is just a reflection of the USGS Native 25k Dem and the Native DEM has these characteristics:

1) Projection can be in NAD27 NAD83

2) Can be in different UTM zones

3) Can have vertical units in feet, meters, decimeters, or centimeters

4) Can have posting of 10m or 30m

Below you will find an image map that will guide you to some of the finest FREE data repositoris, State Clearinghouses, and spatial data libraries around. Some offer free DRGs, others offer free DEMs, many have free DOQQs and aerial photography. Data holding vary from State to State, however, all will provide free, unrestricted access to plenty of data without the need for registrations, no headaches associated with throttled-back download speeds, etc… To access some of our favorite data repositories simply Click on a State. Note: somme of the links below may have changed. For additional pointers to free GIS data repositories please see also our FREE GIS Data Weblog

Note: The image used to create this map was provided by the USGS

DETERMINING WHICH QUADS ARE NEEDED

Locating a quad. Before you go out and grab yourself some data you first need to determine which quad(s) you need. This can be somewhat of a pain unless you have the right tools at your disposal. For frequent users of USGS data you need to get yourself a quad index map, quad database, or some other useful way to identify your area of interest. As a rule, you will be required to know atleast one of several things in order to locate a quad. Descriptive name (eg. ABAJO PEAK), quad number/idenifier (eg. Q3639), or bounding coordinates. Here’s some useful starting points.

DEM Status graphic – The USGS maintains a graphic representation of the status of all of their digital data holdings Status maps are online and available in either html or PDF format Please note that complete coverage of the conterminous US in either 10m or 30m resolution data is not available.

Geographic Names Information Server (GNIS) Query – Query Form For The United States And Its Territories is useful to quickly access and view more information about an area. Submitting a place name will return a host of information including links to quickly view the DRGs on a number of different web servers

My first stop is the Geographic Names Information Server (GNIS), a USGS service. I enter "Electric Peak" for the Feature Name and select Wyoming, since I know it’s in that state. This is what I get back: Mapfinder from USGSquads – MapFinder™ is a PDF (Portable Document Format) based searchable catalog of USGS (United States Geological Survey) paper maps. This handy resource is available as a Java applet and a non-java flavor. Registration [free] is required and a PDF viewer is required to be available on the viewing client.

Topozone – Topzone has a great search utility. For example, I searched on Port Townsend, WA. Resulting hit tells me that the quad name I’m looking for is "Port Townsend South", furthermore, the geographic description is as follows, UTM 10 517829E 5329336N. Finally, the quad name is o48122a7 and the resulting DRG (TIF) file is o48122a7.tif… very handy!

Google Search – pretty much every State in the US has an online data clearinghouse where you can view a quad sheet index for that particular State. Simply use Google and search on "statename usgs quad index". Results will be obvious and take you to places like Oregon, Mass

USGS Mapping Status Page – this site will inform you as to the likelihood of data [USGS] vailability for anywhere in the US. The maps are ser4ved up in PDF and html format and describe data available and in progress. Themes include DRG, DOQ, DEM, DLG, and NAPP.

A number of other places on the web provide free quad index files, however, they may be in a format (or unknown data projection) that makes using the data a challenge.. beware. At the very leat though, these data will prove to be a useful information resource, regardless of the map projection.

Chances are you want to simply get a quick glimpse of the data that’s available for your area of interest. A number of USGS partners have developed and published Internet map servers. Most of these offer visitors the ability to enter a place name or coordinate, then a server displays the requisite USGS topo quad for the area of interest. Additionally, related data products like aerial photos, DOQs, or charts can also be viewed for the area in question. These data servers won’t let you download the data, however, they will give you a preview and perhaps point you to where you can either download of purchase data.

Suggested Map Servers

Terraserver – Resulting from cooperative research by the USGS and Microsoft Corporation, the TerraServer provides free online access to USGS digital aerial photographs, known as digital orthophoto quadrangles, and to digital topographic maps, known as digital raster graphics.

Maptech Mapserver – Online ordering of Digital Mapping and Aerial Photography. Specializing in USGS products – DLGs, DEMs, DRGs, and DOQQs

Terrafly – TerraFly is an interactive "fly-over" application designed to aid in the dissemination and visualization of geospatial data via the Internet. The incorporation of USGS data could make TerraFly one of the largest databases on the Internet. TerraFly will show the user a new and innovative way to explore their digital earth View topos, aerial photos, imagery, and census data

Topozone – TopoZone provides an interactive interface which allows users to view a seamless topographic map and feature database of the entire United States, based on digital raster graphics. The site is accessible to anyone with an industry standard Web browser at no charge.

PART 2 – SDTS, DRG, and DEM developer support, translators, viewers, and tools

See Also the following

State GIS Clearinghouse Directory In order to provide the GISuser with one-click access to various State GIS and geospatial data repositories and clearinghouses, please consult this listing of official State GIS Data Clearinghouses and data repositories.