DPOS Report Questions

[Tyler]

I have a couple questions regarding the DPOS Report for our GPS base station.

1. What determines which CORS stations are used?
a) I have one report from the first day on site which chose 3 CORS stations (P196, P198, P206). The geometry of stations around our base point was not great. The second day after post processing it used 5 CORS (CASR, P183, P188, P196, P198) stations surrounding our base station which I like to see.

2. On the second day DPOS report it only shows residuals of position to 3 of the 5 stations. Why is that?

I have attached the two DPOS reports the first day (5000.1) & the second day (5000.3). I have also attached an image of the CORS stations and Base location for reference.

 

[Alexey Razumovsky]

I have a couple questions regarding the DPOS Report for our GPS base station.

1. What determines which CORS stations are used?
a) I have one report from the first day on site which chose 3 CORS stations (P196, P198, P206). The geometry of stations around our base point was not great. The second day after post processing it used 5 CORS (CASR, P183, P188, P196, P198) stations surrounding our base station which I like to see.

2. On the second day DPOS report it only shows residuals of position to 3 of the 5 stations. Why is that?

I have attached the two DPOS reports the first day (5000.1) & the second day (5000.3). I have also attached an image of the CORS stations and Base location for reference.

A1. DPOS is searching for 5 nearest CORS in a range of 300 km with best geometry factor. CORS that provides data at time of processing.
A2. 2 stations were rejected in adjustment because they did not pass tau test.

 

[Tyler]

A1. DPOS is searching for 5 nearest CORS in a range of 300 km with best geometry factor. CORS that provides data at time of processing.
A2. 2 stations were rejected in adjustment because they did not pass tau test.

Thank you for the response. Your explanation shows why the second day report only shows the residuals of 3 of the 5 vectors because two of the vectors did not pass the tau test. Was the reason there were different CORS stations from the first day and second day because the CORS stations weren't providing data at the time of processing? I am still unclear why it would not be using the same CORS station between day 1 and day 2.

 

[Alexey Razumovsky]

Yes, different CORS provides data at different time.