APRS in the American West
In May of 2006, I did a study of APRS data to find out where
the coverage is (and where the holes are) in the American West
and California. This page has the results of that study.
Click on an image for a larger version
As you can see from the maps, the coverage is concentrated in
population centers and along Interstate and US highways. In California,
the large gaps and areas of spotty coverage can be described as follows,
running clockwise from "noon" (the top center, where I-5 enters
- The entire northeast: Modoc, Lassen, Shasta, Plumas, and Sierra County, except
for I-5, state highway 36, and parts of state highway 299 and 89.
- The Sierra Nevada, running south from Lake Tahoe to Bakersfield and all the
way to the Nevada border (including Death Valley), except for a corridor along US395.
- The Mojave Desert, east of a line from Barstow to Yuma, AZ, with exceptions
for Palm Springs and the I-15, I-10, and I-8 corridors.
- The entire Central Coast, west of I-5 to the Pacific, from
Ventura north to Monterey, except for the US-101 corridor. The
un-covered area includes the Pacific Coast Highway from Hearst Castle to Carmel.
- The entire northwest: Sonoma, Mendocino, Trinity, Humboldt, Del Norte,
and Siskiyou Counties, except for areas near US Highway 101, Interstate 5, and Fort
Some of these areas have spotty or intermittent coverage, not a
complete void. And in some areas without roads, it's likely that no APRS
user has even attempted to get a packet out, so those areas would not
appear as "covered" on maps like this. But anywhere you see yellow
showing through the maps above, you probably shouldn't expect APRS to
reach the Internet.
For this study, I used the APRS archives at
aprsworld.net. The data I got was from January 1, 2006 through March 31,
The data at the APRS archive consists of only one report per hour
from each station heard, so this is a statistical sampling of all APRS
data. It is not 100% complete. If only a small number of mobile APRS
users moved through a given area, it's possible it will falsely appear
not to have coverage because the archives didn't keep any of those
position reports from those stations.
The data I used can not support a study of paths, hop counts, or recommended
routes. Also, I could not tell if any reports were from stations that
were feeding APRS-IS directly (not over the air).
Using text-based scripting tools (sed, sort, uniq) I filtered the
data to include only the American West (30 to 49.9 degrees north, 100 to
124.9 degrees west), and reduced resolution to one tenth of one degree
of latitude and longitude. Those are the points you see on the maps:
each point represents an area a tenth of a degree on a side.
The resulting comma-separated lat/long data file is
19kb compressed. It's manageably small,
with 8475 data points. To get the map images you see here, I used StreetAtlas (version 6) with different icon sizes depending on the map
This study is about APRS packets reaching the Internet via APRS-IS.
The study says nothing about APRS for local over-the-air tracking and
position reporting, for search-and-rescue or special events where no
Internet access is required or desired.
Go to the BestBits home page.
This page was last edited
April 26, 2008.