MassGIS serves most raster data sets in 4x4 km tiles with an ID number. You can find the orthophoto quad index at http://www.mass.gov/mgis/ix_oq.htm. Check this link to read about the ways you can determine the orthophoto quad ID of your location of interest. The following image shows a close up (Amherst town boundaries and OQ outlines) of the PDF version of the MA statewide map:
Figure 1: OQ IDs for Amherst
For example, if you decide you need OQ #117902, you can go to the download area for raster datasets http://www.mass.gov/mgis/dwn-imgs.htm:
Download the 1:5,000 Black & White Digital Ortho Images. As mentioned previously, it is a good habit and a learning tool to read the "data layer description" (http://www.mass.gov/mgis/oqdesc.htm).
QGIS can read Tiff format, but not MrSid. So, you would choose a 5m resolution Tiff image. (Note that 5m resolution image files are not as big as 2m resolution files, 640 KB compared to 4MB). The smaller 5m resolution Tiff image would result in less time to download, more space on your computer, and less time to generate GIS displays. (Always keep these implications in mind, and, when possible, get the least data intensive resolution you need for your application).
Download the .tif (image) file and tfw file (text file header with spatial information) from the ftp site: ftp://data.massgis.state.ma.us/pub/ortho5/.
Select the files 5_117902.tfw and 5_117902.tif and copy them to your work folder (eg., C:\temp\GISdata).
Then, follow the same procedure to download 1:25,000 scale USGS topographic maps (http://www.mass.gov/mgis/ftpquad.htm). Try to navigate to the file using the previous link, but if you have trouble, here is the direct link: ftp://data.massgis.state.ma.us/pub/images/usgs
Note: if you are unfamiliar with some of the available USGS maps at different spatial (map) scales, see http://erg.usgs.gov/isb/pubs/booklets/usgsmaps/usgsmaps.html
There are two principal file formats for vector data - shape files and coverages. The vector data available at MassGIS is in ARC/INFO Export File (.e00) or ESRI Shapefile format. Download the files in Shapefile format. What's the difference of those two formats? Topology. Vector data such as lines and polygons can have a From-To order. This information is useful if you are trying to determine the direction of a stream flow or questions about adjacency (e.g., which polygons share a common border). Arcview shape files don't store topology. Arc/Info coverages or layers do. ArcView shape files are easier to process because they don't store this extra information. This is the major difference between an Arcview Shapefile and a Arc/Info coverage. .E00 is the format for sharing ArcInfo layers.
Let's say that you are interested in land use (zoning) in Amherst and in adjacent areas of neighboring towns. You will want to get two data types from MassGIS: the town boundary and the zoning data.
Town boundaries
To give some context to the layers you have downloaded so far, you will get the Amherst town boundaries. However, there is no data for single town boundaries. What is available is Community Boundaries, a single layer for the entire state, containing the boundaries of the 351 communities in Massachusetts.
Again, go to Download Free Vector Data (http://www.state.ma.us/mgis/dwn-vect.htm)
Choose Statewide layers. Scroll down the table until you find Town Boundaries - no coast.
Download the shapefile data (bndry.exe).
Zoning Layer
Go back to http://www.mass.gov/mgis/download.htm and click "Download Data".
Take a look at vector data availabe by town (this would include layers such as Land Use, Executive Office of Transportation-OTP Roads, 1:5,000 Road and Rail Centerlines and Zoning Districts).
Go to Zoning, under political boundaries and click on the layer description link http://www.mass.gov/mgis/zn.htm
Read through the descriptions of some of the attributes, for example PRIM_USE and GEN_USE.
See that there are also some related tables that one could link to the spatial data, with secondary information, useful for analysis, planning, etc.
Scroll down the table with the names of the towns until you find Amherst. Right-click on zn8.exe and click "save target as". Save the file in a work folder (C:\temp\GISdata)
Now for a moment, let us take a break for a minute from the exercise, in order to explain something. This section of the tutorial is a resource for your future work.
Often you will find free data on the Internet in ArcInfo Coverage format, not Shapefile format. The common way you find these is in the ArcInfo export format (i.e., .e00), which is an interchange file across platforms.
THE IMPORTANT THING TO REMEMBER is that if you see data on the internet that has an extension of ".e00" it means that it is in interchange format, and you will have to convert it back to a coverage or a shape file. This is a common way people serve ArcInfo coverages on the Internet.
QGIS cannot read or convert e00 files, but it can read coverages. ArcInfo export files are not in one of the formats supported by GDAL/OGR libraries either. One option for converting e00 files into ArcInfo coverages is the Import71 Utility (by ESRI, free download, but may not work in linux). You can also try the AVCIMPORT program to import E00 files and create coverages (it is open source software and should work in linux, but has not been tested).
To download ArcInfo layers from MassGIS you need to RIGHT-CLICK and choose "save target as." Save it to your temp directory. MAKE SURE IT DOESN'T PUT A ".txt" ON THE END OF THE FILE NAME. This procedure will save "ArcInfo export" or "interchange" files to this directory.
Note the file structure of ArcInfo coverages. There is a "Coverage name" folder and an "Info" folder. Look at the contents of each of the folders. ArcInfo coverages store the spatial data in the "Coverage name" folder and the attribute data in the "info" folder. This is the proprietary database structure of ArcInfo/ESRI.