Suitable for satellite observations?

[+billwallace]

The text is

Generally, a station is suitable for satellite observations if 
there is a clear and unobstructed view of the sky from approximately 
15 degrees above the horizon at the location of the station.

I have always interpreted this as 15 degrees above the horizon for 360 degrees around the mark but I just noticed that it doesn't actually say that.

 

Any ideas?

 

thnx

[AZcachemeister]

The text is

Generally, a station is suitable for satellite observations if 
there is a clear and unobstructed view of the sky from approximately 
15 degrees above the horizon at the location of the station.

I have always interpreted this as 15 degrees above the horizon for 360 degrees around the mark but I just noticed that it doesn't actually say that.

 

Any ideas?

 

thnx

 

Actually it is pretty subjective.

There have been posts in here where professionals claim good/acceptable results in what I would consider poor to marginal conditions. Depending on the satellite constellation, fully half of the sky could be blocked, but a good observation might be obtained...or not.

 

It's probably best to err on the conservative side.

'I don't know.' is always a valid answer.

[joegeodesist]

Very subjective. I've interfered it as "better than most in the area", Good in Manhattan, NYC is different than in Manhattan, KS.

See http://www.ngs.noaa.gov/marks/descriptors.shtml#visibility

[ArtMan]

Also, I've wondered whether the particular satellites overhead at a given time might be a factor, i.e. at noon on Tuesday I could get a good fix, but not on Friday at dawn. GPS satellites are not geosynchronous, so the subset of the total constellation is in view now might be more favorable than those in view at another time.

 

-ArtMan-

[+billwallace]

thnx,

 

That all sounds about right. I'll just stick with I don't know unless it is obviously a Yes or No

[mloser]

Also, I've wondered whether the particular satellites overhead at a given time might be a factor, i.e. at noon on Tuesday I could get a good fix, but not on Friday at dawn. GPS satellites are not geosynchronous, so the subset of the total constellation is in view now might be more favorable than those in view at another time.

 

-ArtMan-

 

Artman, you are correct. The number and position of the satellites (the "constellation") make a big difference in the signal. Has anyone ever noticed that at times you get great accuracy and other times, even though you are "outstanding in your field" so to speak, you can't seem to get a good signal. Well it all has to do with the constellation--what satellites are visible and high in the sky. GPSWorld discussed this in 2009 There are calculators for determining the best times to get GPS readings. Trimble has a downloadable one.Navcom has an online one. I am sure there are others out there.

 

Edit: found an even cooler one (through a link on the John Deere site). http://navcomtech.com/Support/Tools/satellitepredictor/main.cfm

Edited October 17, 2011 by mloser

[+LSUFan]

Also, I've wondered whether the particular satellites overhead at a given time might be a factor, i.e. at noon on Tuesday I could get a good fix, but not on Friday at dawn. GPS satellites are not geosynchronous, so the subset of the total constellation is in view now might be more favorable than those in view at another time.

 

-ArtMan-

 

Artman, you are correct. The number and position of the satellites (the "constellation") make a big difference in the signal. Has anyone ever noticed that at times you get great accuracy and other times, even though you are "outstanding in your field" so to speak, you can't seem to get a good signal. Well it all has to do with the constellation--what satellites are visible and high in the sky. GPSWorld discussed this in 2009 There are calculators for determining the best times to get GPS readings. Trimble has a downloadable one.Navcom has an online one. I am sure there are others out there.

 

Edit: found an even cooler one (through a link on the John Deere site). http://navcomtech.com/Support/Tools/satellitepredictor/main.cfm

 

Thanks for that link, mloser. I just bookmarked it. Not trying to get off topic too much, has anyone here had much experience with the Russian GPS system (GLONASS)? I've been reading where a lot of the smartphones can use our and their systems......as well as some units able to read both at the same time. I was just wondering how accurate of a reading you could get utilizing both systems at the same time.

Edited October 17, 2011 by LSUFan

[+EdrickV]

As far as I know, there is only one smartphone that supports both (and possibly only one that supports GLONASS) and (unless people are importing them) you'd have to go to Russia to get it.

http://www.whioam.com/in-russia-went-on-sale-smartphone-mts-glonass-945.html

 

On the other hand, the Etrex 10/20/30 support both GPS and GLONASS and are advertised as the first consumer grade GPS receivers that can track both GPS and GLONASS satellites at the same time.

 

Edit:

Quote from an article last month:

The first combined GPS/GLONASS phones will hit the US market "in the coming year," Qualcomm said. The majority of new Qualcomm S2 and S3 processors support GLONASS, which includes the dual-core chips coming out in smartphones like the HTC EVO 3D and T-Mobile MyTouch 4G Slide. Those existing phones won't be able to use GLONASS, though, because the system requires additional radio hardware.

http://www.pcmag.com/article2/0,2817,2392569,00.asp#fbid=pOZ1Ce0ykkm

Edited October 18, 2011 by EdrickV

[southpawaz]

Thanks for that link, mloser. I just bookmarked it. Not trying to get off topic too much, has anyone here had much experience with the Russian GPS system (GLONASS)? I've been reading where a lot of the smartphones can use our and their systems......as well as some units able to read both at the same time. I was just wondering how accurate of a reading you could get utilizing both systems at the same time.

 

Our survey grade Trimble equipment at work is able to use both GPS and GLONASS satellites. With a full combined constellation, I generally am using 13-16 satellites yielding an estimated horizontal accuracy of approximately 1/8" to 3/8". When using only GPS satellites, I am generally working with a constellation of 5-9 satellites and an estimated horizontal accuracy of approximately 1/4" to 3/4". Bringing this around back towards being on topic, one of the major benefits of using the combined constellation is the ability to make measurements within our tolerance for accuracy when there are partial blockages of the sky - I can usually get a good shot up against a building with half the sky blocked when using the full constellation.

[+DukeOfURL01]

In my GIS class, I learned about "mission planning" software that would plan for the best time of day (most GPS satellites) for a data-capturing trip. But I think this was already mentioned. I'll try and come up with the link later.