A Primer on GPS and Trails

1 Abstract

Notes on practical abstracted from NEMBA TRAIL-CREW mailing list discussions.

2 Techniques

2.1 Getting property line data…

...without spending hours at town offices and registry of deeds poring over maps and documents during weekday work hours:

• A lot of towns have digitized their parcel maps in GIS format. Request an electronic copy of this data.
• Go to the town or the regional GIS center (in some areas this is at the regional planning agency). This may be worth pursuing if you need to access tax assesment data frequently, as this will all be available to you in addition to the parcels displayed.
• You can do a half baked job by scanning paper parcel maps from the assessor's office and working with them in CorelCraw or Adobe Illustrator.

2.2 Viewing GIS data once you have it

• Check out the web sites www.geocomm.com, www.gisdatadepot.com, and www.gis.com. these sites contain free data viewers and free programs that translate coordinates from one projection to another.
• The most useful Massachusetts GIS (MGIS) stuff is the orthophotos and the Open Space layer for each town. Note that there is a database associated with the OS map that show useful info - owner, public access, level of protection, etc. All the MGIS data is based upon a UTM coordinate system and this and the map datum needs to be consistant. It is possible to use a consumer GPS to collect data for Arcview but there is a somewhat complex procedure.

2.3 Basic GPS receiver that can upload waypoints to PC

• Garmin eTrex

2.4 Making maps

• Topo! for NH, Delorme Topo USA or 3-D TopoQuads, and Maptech for MA will accept data from GPSs. The Maptech product is deemed best. Good quality USGS topo maps and some ability to manage and edit waypoints and routes. Topo USA maps look more like the Delorme state map books that you may have - a little thin on detail. This type of map program will probably do most everything you might want. All have the ability to interface with almost any GPS you might purchase. An example produced with Topo! Is http://www.bikerag.com/images/MAPS/MA/ma_vietnam_map_by_numbers.jpg.
• http://www.baycircuit.org/amap3.pdf (caution large file) is an example of a map made from various sources including GIS shapefiles using CorelDraw.

3 Tools

3.1 GPS

• Garmin http://www.garmin.com/outdoor/products.html#basic

3.2 Mapping

Prices where given are MSRP.

• Maptech www.maptech.com
• National Geographic Topo! http://maps.nationalgeographic.com/topo/
• Delorme Topo USA ($45-region or $95 for whole US, 30 meter elevation data) http://www.delorme.com/topousa/topo.asp
• Delorme 3-D TopoQuads ($95 per CD, usually one state per CD, but Mass and NH come on one, 7.5’ quads painted on 30 meter elevation data for 3-D views) http://www.delorme.com/quads/default.htm
• A useful GIS viewer is Arc Explorer from ESRI www.esri.com - viewer is under free resources. This will allow you to view all the shapefiles, orthophotos, and UGGS basemaps available at MGIS. Unlike the state viewer, you can save projects. These are just viewers, so to create any reasonable output, Arcview or equivalent is needed.
• MassGIS http://www.massgis.com/
• ArcView ($1,200!) http://www.esri.com/software/arcview/

4 Contributors

• Andrea Newman, EASTMA NEMBA
• Dan Streeter, NSNEMBA
• Mike Tabaczynski