Computerized Topo Maps - Introduction

Computerized Topo Maps
How Good Are They?

Introduction

By Dr. Brad DeLong
Author of 4-Wheel Freedom: The Art of Off-Road Driving

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The bottom line is that topographic maps you can load into your computer are pretty amazing. There are limitations, however, and they take some getting used to.

Whichever program you choose, you should count on spending a fair amount of time with it to learn it thoroughly. Many of the commands and functions are not intuitively obvious. Like many other computer manuals and how-to articles, some parts of this report may not make much sense until you have one of the programs installed and running on a computer in front of you.

I'd suggest you print out these articles and save them. Keep them for reference and use them when you have one of the programs available.

The programs

We'll look at five Topo Map programs.

DeLorme's Topo USA version 2.0 uses vectorized maps to put the entire United States on 6 CDs. For this evaluation we used the Mountain States CD, specifically Idaho.

DeLorme's 3-D TopoQuads is a brand new program that uses a combination of vectorized and rasterized maps. Vectorized maps provide the overview of broad areas, and rasterized DRG topo quad maps come up when you zoom in for detail. DeLorme expects to have the entire US covered by the end of the year. Right now available states and regions are: California (or CA-North and CA-South), Illinois, Maine, Massachusetts, New Hampshire, New York, Vermont, and Washington. Texas and California will each be divided into two sections.

For this evaluation, I used the Northern California collection, which comes on seven CDs, plus an installation CD.

Topo! and Topo!GPS, from Wildflower Productions, contains United States Geological Survey (USGS) DRG (rasterized) topo maps, and currently provides coverage for parts of Arizona, California, Colorado, Connecticut, District of Columbia, Virginia, Georgia, Maine, Maryland, Massachusetts, Michigan, Minnesota, Nevada, New Hampshire, New Jersey, New York, North Carolina, Pennsylvania, Rhode Island, Tennessee, Utah, Vermont, Virginia, Washington, West Virginia, and Wisconsin. In conjunction with National Geographic Trails Illustrated they also produce a TrailSmart series covering nearly all the National Parks in the United States. I used the maps for the San Francisco Bay Area, the Uinta Mountains in Utah, and Yellowstone National Park.

All Topo Maps, from iGage, also contains USGS DRG maps. The data files are part of the All Topo Map CDs, as are the data files in Wildflower Topo!, DeLorme's Topo USA 2.0, and DeLorme's 3-D TopoQuads 1.2. All Topo Maps now provides coverage for Utah, Montana, Colorado, Idaho, and Wyoming.

Fugawi, from Northport Systems, uses 3rd party CD map files, or map files which you have scanned into your computer yourself. USGS DRG topographical maps are available on CD from several companies, including ChartTiff and the Micropath Corporation. We obtained the maps we used in this report from both these sources.

USGS DRG topographical maps are available for the entire US, except California and Tennessee, which have maps available in a different format. DRG means "digitized rasterized graphic" and is the standardized format used for scanning and preparing the maps for use in computers. Paper USGS topographical maps are 7.5 minutes on a side, and the DRG CD maps are the same. The tops and bottoms of the maps cover 7.5 minutes of longitude, and the right and left sides cover 7.5 minutes of latitude. Micropath furnishes them on CDs, each of which contains the quad maps in a block of 1º of latitude by 1º longitude. This works out to 64 topo quad maps on a CD, plus 2 or 3 additional maps of a broader scale. The 7.5' X 7.5' quad maps use a scale of 1:24,000, which we'll explain more later.

California and Tennessee maps are available from Micropath and ChartTiff. They are USGS map scans and look the same, but are not georeferenced to the USGS DRG standard. The California Micropath maps can't be read directly by Fugawi. Each individual quad map has to be specifically calibrated when it's imported into Fugawi. The ChartTiff maps can be read directly.

Rasterized maps are produced from scanning paper topo maps pixel by pixel and create what's known as a bitmap image. Raster maps are scanned much like a photo might be scanned in a scanner attached to a home computer but in a larger format and much more accurate scanner. The vectorized maps consist of georeferenced points and lines connecting the points. If you zoom in enough on a vectorized maps you will see that what appeared to be smooth lines at lower magnification are actually a series of straight lines. Vectorized maps tend to produce more compact files and are seamless (there are no map seams to try to piece together like scanned paper maps).

Each of these five programs has its strengths and weaknesses.

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