MnGCA

rickrich · Geocacher Joined: 06 Jul 2003 Posts: 673

I ran into a cache the other day that required waypoint projection with a precision of .01 miles/degrees, and neither of the Garmin GPSrs we had with us could calculate to that precision. I ended up figuring it out on my laptop.

I made a mental note to seek out a geodetics calculator, and post a link to it on my website for other people who might need to perform such calculations.

I found a very nice one at http://www.gazza.co.nz/geodetics.html

But out of the box that one would only output in DMS format, and we usually use MinDec format. So I hacked it up to add selectable output formats and sent my patches to the author. He hasn't bothered to update his version, so I made my version available here:

http://mngca.rkkda.com/geodetics.html

When inputting coords in MinDec format, just leave the "seconds" field set to zero and type a decimal value in the minutes field and an integer value in the degrees field. Likewise, if you want to input coords in DegDec format, just leave the minutes and seconds fields set to zero and type a decimal value in the degrees field. The help button will also tell you how to input coords. Its a little clunky to do it that way, but the changes to get rid of the three input fields and allow for free format entry of any of the input formats into a single field wil take more work.

Make sure the Output Format is set to MinDec and the Spheroid is set to WGS 1984.

To project a waypoint, fill in the Lat/Lon in the second section of the form. Fill in the distance and the true bearing in the third section of the form. Then click "Calc Point 2". The answer will appear on the left side of the fourth section of the form.

This calculator is single HTML with Javascript web page, so you can lift it and stash it on a local webserver (say, on your laptop) without having to hassle with a lot of other files.

-Rick

Marsha and Silent Bob · Past MnGCA President Joined: 02 Sep 2003 Posts: 6261

RJ · Posted: Wed Mar 03, 2004 1:46 pm Post subject:

My gpsr only projects to whole degrees and tenths of a mile. When doing some of these projection caches, I just project to 8.3 miles if it calls for 8.34 miles and then go to the spot. I then walk ~200 feet further. It works most of the time.

King Boreas · Posted: Tue May 11, 2004 5:25 am Post subject:

Thanks Rick

I don't know when it was added, but Rick's website now has a WAP Portal.

I have a t-mobile cellphone, and during the Winter Carnival I discovered t-zones/web browsing, expecting to be able to get the latest clues. It's probably possible, but I never figured it out, and cancelled my unlimited browsing.

This morning I poked around on the WAP Portal a bit, then while I was "working" I tried connecting to my Share The Land cache, through Rick's site. I like it !

I don't know how much I'll use it, but it's great to know it's available. So, it's not a laptop, and it's not a hiptop. I'll call it my wristtop.

Apparently I can use the phone to log a cache. I'll try that later.

rickrich · Geocacher Joined: 06 Jul 2003 Posts: 673