Wednesday, November 02, 2005

GPS MeterPDA: How many feet in a minute

Wondering about how many feet there is in a second or minute of a degree I came across GPS MeterPDA, developed in Barcelona, Spain by Juan A Luna. For the actual answer go down on this post.

GPS MeterPDA is a neat commercial package with a 15-day trial period that can help you measure distances and areas in either meters/hectares or feet/yards. You can purchase a license for 32 euros, or US35$ at PocketGear.

I installed version 1.0.8 on a PPC 2003 (minimal version requirement) and it seemed to work just fine. I walked along the San Lorenzo River and start marking points along the way. The package will display the total distance covered and the distance from the last point.

If you closed an area, it will also display its current value. You can save a project in its binary format (.gtm) and export it as coordinates in text and .dxf (Drawing Interchange Format used in CAD):

Datum,WGS 84
WP,D,1,36.975517,-122.023780
WP,D,2,36.975868,-122.022468
WP,D,3,36.976377,-122.022572

Besides WGS84 you can select among up to 270 datums. You can also work with UTM coordinates. For precision you can obtain several readings from the GPS receiver for a given point and use its average. You can also verify the distance between saved points from a list view.

And the answer is...

And if you are still wondering about how many feet in a second, according to this USGS webpage here is the answer:

"How much distance does a degree, minute and second cover on your maps?

The distances vary. A degree, minute or second of latitude remains fairly constant from the equator to the poles; however a degree, minute, or second of longitude can vary greatly as one approaches the poles (because of the convergence of the meridians). At 38 degrees North latitude, one degree of latitude equals approximately 364,000 ft (69 miles), one minute equals 6068 ft (1.15 miles), one-second equals 101 ft; one-degree of longitude equals 288,200 ft (54.6 miles), one minute equals 4800 ft (0.91 mile), and one second equals 80 ft."