Frequently Asked Questions

Do we need L1 and L2 bands?
If you are using a RINEX logger as a base station and you plan to use an online processing service like AusPos or OPUS to provide the coordinates of this base station, that service will require both L1 and L2 bands to provide an accurate position. The RINEX file you provide to Propeller needs to be updated with these coordinates and should contain at least L1 band observations.

Do you make use of other constellations? i.e. GLONASS, Galileo etc.

We only use GPS for reasons outlined in this article:

What is the minimum observation time?
Propeller requires a minimum of 45 minutes observation data, but we prefer 60 to 90 minutes. 

What datum(s) should the observation point be recorded in?

 We can support any datum that uses the GRS80 ellipsoid. However, we recommend using the local datum to obtain correct projected map coordinates. Here are some common datums that comply with that requirement:

Australia: GDA94
Europe: ETRS89

Where on the AeroPoints are the Z values in the reports that we receive?

Z values are measured from the top of the AeroPoints. This is because when they are used as Ground Control Points and manual processing is required, we align images using pixels corresponding to the top of the AeroPoints. We recommend using that data as it is a correct reading of the surface level of that point in the corresponding images. If you need to know the height of the ground underneath the AeroPoint, you can subtract the thickness of the AeroPoint (32mm) from the survey report's height data, by downloading the survey report in CSV or excel format  and reducing the "NAD83 (2011) Height (m)" (usually column G) and "NAVD88 Height (m)" (usually column J) values for each AeroPoint by .0032.

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