California county lines in your GPS? you county listers can now have them
- Howdy CalBirders?
I made an announcement a few days back regarding this topic on the County
Birders listserv. I thought that the wider audience of CalBirds may be
interested as well.
Joseph Morlan has been kind enough to host the file. The direct link is:
California County Lines/Listing Boundaries file
If you are a county lister and often ask "What county is that bird in?"
then this file is for you.
In this day of high-tech devices available to ordinary citizens, there is no
reason why listing boundaries can't be precisely codified in map form so
that when you are in the field you can know when you cross over the line.
This is my first stab towards that end and I consider Phase 1 complete. In
this file you will find county boundaries for all of California's counties
and offshore islands out to 3nm. The data come from two sources. The first
source was more precise and the second source drew the county lines to the
3nm buffer. I really don't know the provenance of the first coverage but I
got it from Pablo Herrera and it is more precise because it more closely
follows the old thalweg of the rivers and creeks which defined the counties
in the 1800's. It also follows the ridgelines more closely in those
instances where ridges define the boundaries. The second source was
downloaded from Tiger Line which is curated by the Census Bureau. I opted to
use this for the coastal counties because it continued the county line
offshore to the limit of what is county jurisdiction. Actually what I have
done is retain both versions, so that is why you will find two shapes for
all the coastal counties. Each island group also has their own shape. Note
that the shapes in the Census Bureau dataset contain some errors. When you
find errors, I would like these brought to my attention if you think they
deviate more than 30 meters from reality. I am currently working on taking
the county lines further off shore. My goal for Phase 2 is to take them all
the way to the 200nm limit.
This file is in GDB format. It is a format which you can use to load spatial
data into Garmin's MapSource software and then into their GPSs. If a GDB
file doesn't interface with your favored GPS interface program. I'd suggest
downloading GPSBabel <http://www.gpsbabel.org/> which is a file type
converter. It surely will have what you need for turning it into a format
which you can use. Once the file is loaded to your GPS, these images (see
webpage) are what you can expect.
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