GIS Data for Download
All of the data available for on-line viewers such as MassGIS - plus world's more - is available for available for one-time download as GIS “shape files” over the Internet.
Once downloaded, the data can be used offline, which makes it a better solution for people who don’t have easy access to broadband, or for folks like me who are obsessive about this stuff. There's simply much mare data available in shape files than there is in web viewers.
You’ll need to download and install special viewing software on your computer. The principal one is ESRI’s ArcExplorer available at:
http://www.esri.com/software/arcexplorer/
Be warned that ArcExplorer is a Win95-era piece of software. Among its many quirks, it doesn't work properly with the current Windows extended-length filenames or file system. For example, a filename such as VT_Streams.AEP (AEP is the extension for an ArcExplorer workspace) gets turned into VT_STR~1.AEP the second time you save it, which is the DOS-compatible filename that all current Windows versions use "under the covers". Similarly, ArcExplorer doesn't recognize "My Documents" as a special directory. Instead it will make you navigate from the C: drive root directory, through a fairly tortuous path. You may want to consider storing your AEP projects and data on the root directory, so you can avoid this.
For those of you who grew up with DOS, it's inconvenient as hell, but easy enough to work around. If you don't know this kind of stuff, ArcExplorer may throw you totally for a loop. You’ll need to be pretty computer proficient and patient to get it to work and, if you're like me, spend hours of trial and error before getting useful results.
But given all the data that's available, it's more than worth it. Many of the maps in this website were created using ArcExplorer, despite all of its quirks and limitations. For example, check out the maps of Massachusetts and Rhode Island on their respective pages.
Here we show an ArcExplorer "workspace" that provides streams, roads and lakes for New Jersey (divided up by county). You check the box in the layer to display it, or turn it off, similar to how you controlled the web viewer.
The base layer in the screenshot show above is the bedrock lithology of NJ, downloaded from the NJ-GIS clearing house. That whitish band next to the cursor is one of the largest limestone formations in NJ. You can see three tributaries of the Little Flat Brook that cross it.
It looks simple once you have the workspace displaying this way, but you have to set up each layer, and your tools to do so (in this free viewer) are very primitive. Unfortunately, the top-end ESRI desktop, which gives you all the tools you would ever want and more, costs $15,000. So unless you have a friend in a GIS department, you're probably stuck with ArcExplorer.
Click here for a tutorial (1.7 MB), which explains how to set up ArcExplorer to create maps of SE US trout streams. A sample map is here (3.4 MB).
The reason for downloading it is the unbelievable amount of data which is available for free which you can view (sometimes poorly) with this tool. Besides the US Federal Government, virtually every college and university (from community college on up), every state government, and every medium-sized or larger city has a GIS department. MOST post the results of their work on the Internet as ESRI "shapefiles", which can be freely downloaded by anyone who cares to find them. (A principal exception is the State of NY, who password protected their GIS clearinghouse in a fit of post 9/11 concern about terrorists. However, a lot of useful information is openly available from Cornell and SUNY).
Expect to be frustrated, as well as amazed, by what's available. For example, there's a Pennsylvania shape file which plots the location and lists the results of EVERY fish survey conducted by the PA Fish and Boat Commission between 1975 and 1995. The meta file which describes it is here:
http://www.pasda.psu.edu/documents/metadata/clearinghouse/pfbc-pafish.xml
Unfortunately, it appears to be impossible to display properly in ArcExplorer: the best I've been able to do is plot the location of every fish sampling, and read the species found therin manually. But there's no way I can figure out in ArcExplorer to display only the surveys which found trout species. IF YOU'RE A GIS PRO, AND WOULD LIKE TO HELP WITH THIS PROJECT, PLEASE CONTACT ME!
Nevertheless, despite the frustrations, there is a wealth of information which CAN be displayed effectively. For example, the workspace I set up for myself for NJ is MUCH more useful than the NJ online viewer. For states which don't provide a web-based viewer, it may be the only practical way to view state information which the USGS web viewer or topo maps may not supply.