GPS Planning Software?

[Badmachine]

Besides the Trimble planning software, are there other easy to use planning software products that allow one to view satellite visibility and GDOP for various dates and locations?

 

Thanks

[+ecanderson]

Bugger, bugger, bugger.

 

Yes. Someone here, ages ago, tossed out a url for a site that allows you to predict future ephemeris conditions based upon your latitude/longitude and point in time. The site would bar-graph the estimated GDOP results -- if I recall correctly, across any specified 24 hour period.

 

I have searched all over for that and have come up blank. I'd certainly appreciate it if anyone who is familiar with that site would repeat its location for me, too.

[+tec_64]

http://www.leica-geosystems.com/en/GNSSGPS-Systems_4224.htm

 

Same as the camera company, only the survey equipment division.

 

There should be a Software link down near the bottom on the left.

 

Wayne

[+user13371]

Been looking for this myself. Wouldn't that be a COOL iPhone or Android app?

[+ecanderson]

Been looking for this myself. Wouldn't that be a COOL iPhone or Android app?

Yeah -- doggone it, it's out there somewhere. When I first visited, I popped in some random dates and was surprised to see the variability that exists, even with 24 birds in the air at a time. You can certainly see times when your GPS is going to have a bad hair day.

 

I still have one of the graphs that I did back when I still had the link, but didn't have the stuff turned on in the footer when I printed the page, so have zero clue about the URL. Rats, rats, RATS!

[+ecanderson]

Finally found it again!!!

 

Site produces projected GDOP, PDOP, VDOP and HDOP data for your choice of location and time.

 

http://www.navcomtech.com/Support/Tools/sa...dictor/main.cfm

[+user13371]

(delete)

Edited October 15, 2010 by lee_rimar

[+user13371]

EC, I'm not sure how this thing does its calculations, or if it does them correctly and consistently.

Try this and see what happens:

 

Put in your home coords and time zone. Look at the DOP graph, especially what time DOP spikes for you.

Change the latitude to 10 degrees south of where you are and look at it again.

Then 10 north of your location.

NOW put your home coords back in -- does the graph look the same as your original entry?

 

It didn't for me. Maybe I'm using it wrong?

I'm gonna have to load up Trimble Planning at work and see which graph is "right."

[Grasscatcher]

What's NOT good in my opinion is that you have to just "assume" it's giving you the correct info, with no way to double check (that I can find).

 

Even with Trimble Planning software, I ALWAYS go to the specific visible sats page and verify that my GPS is "seeing" the exact same sats that the software "says" it should see at my present location. That's just a double check that all settings are correct.

[+ecanderson]

No way to verify, but the "raw" data from the elevation chart (tab 1) certainly looks real enough. If they've got that right, they've probably got the position data correct, and GDOP should be accurate.

 

"NOW put your home coords back in -- does the graph look the same as your original entry?"

 

For some reason, not at first, no. But if you go to the next or previous day and then back to the original day, it looks just like it did originally. Not sure why. If you tweak the location, it acts like it's incrementing a day accidentally or something, and you have to get it back on track by moving "back" to your original day.

 

Will be interested to hear what your Trimble software says about it.

[+user13371]

...If you tweak the location, it acts like it's incrementing a day accidentally or something, and you have to get it back on track by moving "back" to your original day....

Ah, I didn't try punching the days forward and back.

 

I may not get a chance to load up Trimble Planning at work today--I took it off a while ago and haven't had reason to put it back yet (and today is busy). Do you run it on your own machine also?

[+ecanderson]

Do you run it on your own machine also?

Negative, which is why I was so amused to find that web site a while back. No access to anything else to give me DOP data.

 

Sometimes the configuration is just SO strange that I use my TomTom to take a screen shot. Once in a rare while I get a real "cluster" overhead ... not good caching moments! Had a really interesting configuration one day where it looked like about 9 of them were lining up in almost a straight line. That was different.

[Badmachine]

Finally found it again!!!

 

Site produces projected GDOP, PDOP, VDOP and HDOP data for your choice of location and time.

 

http://www.navcomtech.com/Support/Tools/sa...dictor/main.cfm

 

If I'm not mistaken, I notice that this tool doesn't provide data for years previous to 2010.

 

Also, satellite visibility graphs for certain coordinates, date and time generated about 1.5 years ago by Trimble's software differ significantly from graphs generated today for the very same coordinates, date and time.

 

[Badmachine]

Finally found it again!!!

 

Site produces projected GDOP, PDOP, VDOP and HDOP data for your choice of location and time.

 

http://www.navcomtech.com/Support/Tools/sa...dictor/main.cfm

 

If I'm not mistaken, I notice that this tool doesn't provide data for years previous to 2010.

 

Also, satellite visibility graphs for certain coordinates, date and time generated about 1.5 years ago by Trimble's software differ significantly from graphs generated today for the very same coordinates, date and time.

 

[+user13371]

BadMachine, is this a problem? Educate me.

 

I typically use this kind of planning software for current and near term future activities. I expect satellite visibility to change day to day (hour by hour) -- and predictions only to be valid for a limited time going forward, maybe a few weeks.

 

Do you have a different usage or expectation? How will you be using prior years' data? And how/why would you expect a graph generated a 18 months ago to match one generated today?

[Badmachine]

BadMachine, is this a problem? Educate me.

 

I typically use this kind of planning software for current and near term future activities. I expect satellite visibility to change day to day (hour by hour) -- and predictions only to be valid for a limited time going forward, maybe a few weeks.

 

Do you have a different usage or expectation? How will you be using prior years' data? And how/why would you expect a graph generated a 18 months ago to match one generated today?

 

Being a novice (or "tadpole" by board standards), I may rightly or wrongly expect that visibility data for a date and location in 2001 obtained 18 months ago would remain unchanged if the same data was requested 1 day ago by the same Trimble software. I had thought such data was an unchanging "snapshot" of visibility conditions for a given place and time in the past.

Edited October 25, 2010 by Badmachine

[+user13371]

I guess I still don't understand what you're after there. I hadn't even thought of using either of these (Navcomtech or Trimble) planning tools to back-calculate positions from years ago -- and I wouldn't worry if they got it wrong. I'd be more concerned if it didn't correctly project the current positions for today and for the upcoming week or two, based on current almanac data.

 

Do Navcomtech and Trimble planning agree with each other on near term future predictions? I've already noticed N gives goofy results if you switch locations during a session (that is, get predictions from one location, then re-enter a new one, and go back to your original location). I'm not sure I trust this tool yet at all.

Edited October 25, 2010 by lee_rimar

[Grasscatcher]

Is it strictly a variation between the two different programs that you're seeing, or are you saying that Trimble's results obtained recently (but backdated) don't agree with Trimble's results (previously obtained)for the same time and date.(which at that time were a prediction)?

 

I've always found Trimble Planning to be very accurate, BUT.....I've never tried to compare a newly acquired chart to one that I previously obtained.

 

I always ....always print out a chart/list of which sats that I "should" be seeing at my present location/time and go outside and physically veriify on my GPS that , in fact, those are the ones that I "am" seeing.

 

That's just a double check to eliminate "operator error" in settings.

Correct almanac, time zone, DST, etc

[Badmachine]

Is it strictly a variation between the two different programs that you're seeing, or are you saying that Trimble's results obtained recently (but backdated) don't agree with Trimble's results (previously obtained)for the same time and date.(which at that time were a prediction)?

 

In my case, 18 months ago Trimble generated certain visibility data results for a particular place and time. When visibility data for this place and time were searched again yesterday using Trimble, the visibility data graphs were substantially different.

 

[+ecanderson]

Is it strictly a variation between the two different programs that you're seeing, or are you saying that Trimble's results obtained recently (but backdated) don't agree with Trimble's results (previously obtained)for the same time and date.(which at that time were a prediction)?

 

In my case, 18 months ago Trimble generated certain visibility data results for a particular place and time. When visibility data for this place and time were searched again yesterday using Trimble, the visibility data graphs were substantially different.

 

There are a couple of reasons why this shouldn't be surprising. Example: At least three of the existing satellites were moved into new orbits in January of this year as they began to move SVN24 into its orbit. There is no way the Trimble data from 18 months ago could or would have projected that, and there's therefore no reason that those projections should match anything generated now.

[Badmachine]

Is it strictly a variation between the two different programs that you're seeing, or are you saying that Trimble's results obtained recently (but backdated) don't agree with Trimble's results (previously obtained)for the same time and date.(which at that time were a prediction)?

In my case, 18 months ago Trimble generated certain visibility data results for a particular place and time. When visibility data for this place and time were searched again yesterday using Trimble, the visibility data graphs were substantially different.

 

There are a couple of reasons why this shouldn't be surprising. Example: At least three of the existing satellites were moved into new orbits in January of this year as they began to move SVN24 into its orbit. There is no way the Trimble data from 18 months ago could or would have projected that, and there's therefore no reason that those projections should match anything generated now.

Thanks.

 

If I understand correctly, such satellite relocations would affect the outcome of these two separate Trimble estimations, even if they were both for a common date and location in 2001?

Edited October 26, 2010 by Badmachine

[+user13371]

BadMachine: There's enough variability in the GPS satellite orbits that the almanac (the rough data used by the planning program) is typically updated every 24 hours*. Predictions made more than a few weeks out aren't likely to be accurate. If you run a prediction months apart using different almanac data, you will certainly get different results -- even if both predictions are for one specific time/place.

 

---

* Source: http://en.wikipedia.org/wiki/GPS_signals#Almanac

Edited October 26, 2010 by lee_rimar

[+northernpenguin]

Been looking for this myself. Wouldn't that be a COOL iPhone or Android app?

 

Wouldn't something like Hidden Sky(iTunes Link) fill this niche?

 

I used to use PocketSat+ on my Windows Mobile device for satellite prediction for Ham radio stuff too. Had to periodically download an ephemeris file from NASA to be accurate - you sure weren't looking for next June but if you're planning to ping the ISS over Ham radio tomorrow night, this was just the ticket

 

Edit - looks like PocketSat is available for iPhone/iPod Touch nowadays too !

Edited October 26, 2010 by northernpenguin

[+user13371]

... HiddenSky ... PocketSat3 ...

Will either of these give DOP calculations plotted out in advance?

"Show me where the satellites are" is only part of what a GPS planning tool does.

[+northernpenguin]

... HiddenSky ... PocketSat3 ...

Will either of these give DOP calculations plotted out in advance?

"Show me where the satellites are" is only part of what a GPS planning tool does.

 

PocketSat will let you predict locations for objects in the future. Not sure what DOP is so I can't answer that very well without some Googling. I've used it to plan out ISS spotting nights in the past (vs looking up and seeing what's there at the time - far more handy to know when to bother heading out to the dark beach in the first place).

[+ecanderson]

If I understand correctly, such satellite relocations would affect the outcome of these two separate Trimble estimations, even if they were both for a common date and location in 2001?

Roger that -- and that is why hindsight data, especially over a long period of time, is NOT very likely to be valid. Think about it for a sec. For dates prior to current, Trimble is either projecting from current orbital information, or isn't "projecting" at all, and is using the true history (which would require some monster tables!).

 

In the latter case (using real historical ephemeris data), the results would always be the same - a reflection of what actually happened. But that's not the case. Instead, it's trying to project backward from current information, which is assured to provide different results due to changes in orbits in the interim. Projecting backwards at two different points in time (especially projections taken 18 months apart that span a deliberate change in the orbits of some of the satellites!) would provide two very different sets of results. The same problems can occur when projecting forwards if orbital changes occur in the interim (either intentional or through drift) between the two points where the projections are made. The projection taken closer to the target date will always be preferred.

Edited October 26, 2010 by ecanderson

[+user13371]

...Not sure what DOP is so I can't answer that very well without some Googling...

In case I beat you to da Google...

 

DOP == Dilution of Precision == A shorthand way of saying how useful (or not) the information from GPS satellites is. It's based not only on how many sats are in view, but also their overall geometry as seen from your location.

 

A more detailed explanation, with all the hairy math, is here:

http://en.wikipedia.org/wiki/Dilution_of_precision_%28GPS%29

[+northernpenguin]

...Not sure what DOP is so I can't answer that very well without some Googling...

In case I beat you to da Google...

 

DOP == Dilution of Precision == A shorthand way of saying how useful (or not) the information from GPS satellites is. It's based not only on how many sats are in view, but also their overall geometry as seen from your location.

 

A more detailed explanation, with all the hairy math, is here:

http://en.wikipedia.org/wiki/Dilution_of_precision_%28GPS%29

 

Ok, I'm pretty sure those apps won't give you THAT information. They're more for showing off (Visible Sky) and predicting celestial objects to bounce Ham radio signals off than for GPS precision stuff, unfortunately.

 

Hey the iPhone SDK's only $99 if you wanna write one

[+user13371]

Actually, the SDK is free -- it's a developer's certificate, needed for publishing your apps, that costs $. And I have looked at it. I just haven't been able to wrap my brain around Cocoa in general or iPhone development in detail. Yet.

Edited October 26, 2010 by lee_rimar

[Badmachine]

If I understand correctly, such satellite relocations would affect the outcome of these two separate Trimble estimations, even if they were both for a common date and location in 2001?

Roger that -- and that is why hindsight data, especially over a long period of time, is NOT very likely to be valid. Think about it for a sec. For dates prior to current, Trimble is either projecting from current orbital information, or isn't "projecting" at all, and is using the true history (which would require some monster tables!).

Makes sense.

 

Thanks

[+GPSlug]

Ashtech has launched a new web-based (javascript) planning tool. It even lets you put in an obstruction profile.

 

For dates prior to current, Trimble is either projecting from current orbital information, or isn't "projecting" at all, and is using the true history (which would require some monster tables!).

You can download historic almanac files from the U.S. Coast Guard. But if I recall correctly, and if Trimble's planner hasn't changed since I last used it, you would need to manually download and open an old almanac file for the time you're interested in.

[+ecanderson]

You can download historic almanac files from the U.S. Coast Guard. But if I recall correctly, and if Trimble's planner hasn't changed since I last used it, you would need to manually download and open an old almanac file for the time you're interested in.

If the historical almanac data were being used, it wouldn't matter when you asked for that history -- the information would be the same. The fact that it isn't the same is what demonstrates the results are an attempt to project backward in time, not a search of an external database for the info.

[Badmachine]

Ashtech has launched a new web-based (javascript) planning tool. It even lets you put in an obstruction profile.

 

For dates prior to current, Trimble is either projecting from current orbital information, or isn't "projecting" at all, and is using the true history (which would require some monster tables!).

You can download historic almanac files from the U.S. Coast Guard. But if I recall correctly, and if Trimble's planner hasn't changed since I last used it, you would need to manually download and open an old almanac file for the time you're interested in.

 

Could someone explain the titles of these U.S. Coast Guard almanac links? Also, when downloaded these files dont seem to open without an unknown program.

 

"ALMANACS; SEM; YUMA; NANUS; OPS ADVISORIES"

 

Apart from this information, is there any other record (i.e.: government) that contains GPS satellite orbit/location information for a previous date in 2001?

 

Thanks in advance.

 

[+GPSlug]

You can get Trimble Planning here. It will take the Yuma format files.

 

The 2001 files here are listed as <DayOfYear>.ALM. Google "day of year" for any number of calculators to compute the day of year from calendar date. Pick the closest file on or before the day in question and rename it to whatever.YUM so Trimble Planning knows what to look for.

 

Then in Trimble Planning, select Almanac|Clear, then Almanac|Import|YUMA and get the file you downloaded. It should now be using an almanac that would have been received on that date.

[Badmachine]

You can get Trimble Planning here. It will take the Yuma format files.

 

The 2001 files here are listed as <DayOfYear>.ALM. Google "day of year" for any number of calculators to compute the day of year from calendar date. Pick the closest file on or before the day in question and rename it to whatever.YUM so Trimble Planning knows what to look for.

 

Then in Trimble Planning, select Almanac|Clear, then Almanac|Import|YUMA and get the file you downloaded. It should now be using an almanac that would have been received on that date.

 

Thanks GPS Lug.

 

When I go to the USCG site, under YUMA files, I download the file for the desired date but the numbered files under "YUMA" have an ".ALM" extension. When following the "Almanac|Import|YUMA" steps you provided, Trimble requires files with ".YUM" extensions.

 

An ".ALM" file for a specific date when used by Trimble provide just basic satellite numbers information but doesn't seem to allow one to use them to obtain visibility and GDOP figures for a given time and location for that date.

Edited December 20, 2010 by Badmachine

[+user13371]

I can't believe there still isn't such an app for the iPhone. Anything for Android yet?

[Badmachine]

You can get Trimble Planning here. It will take the Yuma format files.

 

The 2001 files here are listed as <DayOfYear>.ALM. Google "day of year" for any number of calculators to compute the day of year from calendar date. Pick the closest file on or before the day in question and rename it to whatever.YUM so Trimble Planning knows what to look for.

 

Then in Trimble Planning, select Almanac|Clear, then Almanac|Import|YUMA and get the file you downloaded. It should now be using an almanac that would have been received on that date.

 

Noticed that running the 2001 almanac files with Trimble Planning while under the ".ALM" and ".YUM" extensions generate somewhat different visibility and DOP results.

 

Which visibility and DOP results would be considered more reliable? The ".ALM" or ".YUM"?