Best Time Of Day For Reception

December 10, 2003

I'm thinking of hiding my first cache. Since the coordinates taken when placing the cache are critical for others to find the cache, I was wondering what time of day would give me the best accuracy.

Thanks

9.2k · December 10, 2003

There's no general answer to that. The satellites don't have an exact 24hr orbit, so the constellation at, for example 12 noon, won't be the same two days in a row. And, of course, where you are also makes a difference.

There are websites that will show you satellite constellation at a particular.

1.1k · December 10, 2003

Being a dynamic system things can be quite variable during the day and from day to day depending on the status of the constellation for a particular time at a particular place.

There can be quite a bit of difference in the "best" time even with one satellite shutdown for some reason. Also for a particular place/time obstructions can come into affect, even briefly, that might affect the results.

There is planning software freely available, which will give an "indication" of when is the better time to be at a certain location.

Cheers, Kerry.

Edited December 10, 2003 by Kerry.

December 10, 2003

Try this lot for some planning help:

Download satellite tracking software here: http://www.heavenscape.com/download.html

Download TLE's(two line elements) here: http://celestrak.com/NORAD/elements/

Input your location co-ordinates and you can look at projected passes of the satellites

Hope it helps

December 10, 2003

The best way to be as accurate as possible is mark your waypoint location several times and compare the result then take the average.

You might be surprised at the variation you get in the same spot. The area has a lot to do with it too,like lots of trees will have a factor on reception and results.

When in dought make sure to include some clues to help the finders if the Lat/Lon isn't exactly on the money.

5.7k · December 10, 2003

I've had good results with Magellan Meridian and Sportrak models by just letting them do their averaging. All I do is hold the GPS still for at least 1 minute and then wait another 30 seconds to see that the current reading is stable. The main data screen shows how long the unit has been averaging. I rarely have had complaints about the coords I post.

--Marky

December 10, 2003

I use Leica Geosystems satellite geometry software (There are several others). Just using the default parameters seems to give a pretty good indication of how favorable a particular time and day is on the ground.

In practice, when I want to know how good a fix is, I record the exact time of the fix and list the satellites being received. Then plug that into the software with a zero degree cut-off angle and read off GDOP, looking for a value well under 3.0, (2.0 if possible). Remember, one good fix is much better than the average of a bunch of crappy ones, so auto-averaging is generally not very useful. (Sorry if this raises the hackles of the averaging people. So be it). Likewise, the average of a bunch of good fixes (low actual GDOP) spread over a range of days/times/constellations is even better yet. Don't worry if you just can't seem to get these low numbers. In the real world, trees, mountains, buildings, etc. can conspire to prevent your cache from being located to the nearest .001 minute. Just add a star to the difficulty rating and leave it at that.

The two links given by fivegallon appear to be for people that want to find satellites with their telescopes. This won't be much help in determining good satellite geometry for navigation.

Ah, I see you are from BanCoober Eyeland. My above warning about trees and mountains is important

Edited December 10, 2003 by blindleader

December 10, 2003

Blindleader,if you take a closer look,you will see on the second link that there are TLE's for "GPS Operational" satellites.When these TLE's are loaded,a "batch prediction" can then be run giving information as to what satellites should be in sight of the co-ord's you enter.

I don't have a telescope,but the program still works for me

5.3k · December 10, 2003

The satellites don't have an exact 24hr orbit, so the constellation at, for example 12 noon, won't be the same two days in a row.

Well, you are half right. The satellites have an orbital period of 12 hours such that they complete 2 orbital revolutions within a 24 hour period while the earth rotates 360 degrees. This results in a trace of the satellite orbit on the earth's surface which will repeat itself daily. So, the constellation at noon will be the same two days in a row.

4.7k · December 10, 2003

The best way to be as accurate as possible is mark your waypoint location several times and compare the result then take the average.

i'm going to suggest that when you take averages, you eliminate the outliers first. i've had some terrible luck averaging, but good luck with taking multiple waypoints from one spot and ten checking to see what makes sense. i also often check the coords against available online maps.

9.2k · December 11, 2003

So, the constellation at noon will be the same two days in a row.

Not at noon according to your clock. GPS satellites have a 12 hour orbit. But they're sidereal hours. That means that the time a satellite returns to the same position varies about 4 minutes every day.

But the be absolutely precise, if you ask when a specific satellite constellation will repeat, the answer is pretty much never.

1.1k · December 11, 2003

.... So, the constellation at noon will be the same two days in a row ....

No not so there's a precession factor of about 4 minutes, each and every day.

Cheers, Kerry.

3.3k · December 11, 2003

i'm going to suggest that when you take averages, you eliminate the outliers first. i've had some terrible luck averaging, but good luck with taking multiple waypoints from one spot and ten checking to see what makes sense. i also often check the coords against available online maps.

I agree. If you take 10 readings at various times, and get a tight grouping of four or five coords and you see that the remaining coords seem randomly scattered about, just average the four or five good, tight coords! One bad apple can spoil the bunch! Five or six of them can mess up someone's caching experience. :lol:

1.1k · December 11, 2003

Many variables with planning and time of day but Some comments on Time of day

Cheers, Kerry.

December 13, 2003

Hear is a program from a hi end commercial GPSr manufacturer that plots the best times to git the most satelites and its free. http://www.trimble.com/planningsoftware.html

December 13, 2003

Hear is a program from a hi end commercial GPSr manufacturer that plots the best times to git the most satelites and its free. http://www.trimble.com/planningsoftware.html

I use that. It's a lot of fun to play around with. :lol:

3.3k · December 14, 2003

Hear is a program from a hi end commercial GPSr manufacturer that plots the best times to git the most satelites and its free. http://www.trimble.com/planningsoftware.html

:lol: Well, I just tried installing it and it crashed my computer during the installation! My screen went black and then the computer rebooted. The autocheck program started running and reported MASSIVE corruption! About 514MB of data on my hard drive has been stored in folder "FOUND.000"

Install this program at your own risk! You have been duly warned.

December 15, 2003

Multiply the hour of observation by two. Add the number twenty four to the total. Then divide the total by two and subtract the hour of observation. That'll tell you the precision factor of the constellation +/- 0.002777778

Edited December 15, 2003 by gallahad

December 15, 2003

Hear is a program from a hi end commercial GPSr manufacturer that plots the best times to git the most satelites and its free. http://www.trimble.com/planningsoftware.html

Well, I just tried installing it and it crashed my computer during the installation! My screen went black and then the computer rebooted. The autocheck program started running and reported MASSIVE corruption! About 514MB of data on my hard drive has been stored in folder "FOUND.000"

Install this program at your own risk! You have been duly warned.

I installed it several day ago and had no problems, go figure.

9.2k · December 15, 2003

Hear is a program from a hi end commercial GPSr manufacturer that plots the best times to git the most satelites and its free. http://www.trimble.com/planningsoftware.html

Well, I just tried installing it and it crashed my computer during the installation! My screen went black and then the computer rebooted. The autocheck program started running and reported MASSIVE corruption! About 514MB of data on my hard drive has been stored in folder "FOUND.000"

Install this program at your own risk! You have been duly warned.

I installed it several day ago and had no problems, go figure.

I installed it without a problem, but when I uninstalled it, all it did was remove the icon from the start menu. It didn't remove any of the program files (had to do it manually).

3.3k · December 27, 2003

Hear is a program from a hi end commercial GPSr manufacturer that plots the best times to git the most satelites and its free. http://www.trimble.com/planningsoftware.html

Well, I just tried installing it and it crashed my computer during the installation! My screen went black and then the computer rebooted. The autocheck program started running and reported MASSIVE corruption! About 514MB of data on my hard drive has been stored in folder "FOUND.000"

Install this program at your own risk! You have been duly warned.

I dunno... must be my 'puter. I just installed a new 200GB hard disk about a month ago. Could just be a flaky drive. I think I'm gonna start backing up a bunch of important data!!! :unsure:

Best Time Of Day For Reception

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