need to collect enough raw data on the point you have to use. Enough means several hours, because NGS and AusPos will search for the nearby known GPS base stations, but sometimes the closest is 500-1000 km far from your point. The longest your data is the best chance to get fix position from the mentioned services. 4 hours was enough for me to calculate a vector from Hongkong to Hanoi (800 km), but 12 hours was not enough from Bahrain to Tehran (1100 km)
The logging rate must be about 1 per minute, or 1 per 3 minute if you want to use these external services.
If you can find base stations closer to your point, and you are processing the data with your own sw. such as Trimble TBC, you need to log raw GPS data at the same rate which the Reference stations are using (1/sec..1/15sec, etc), and the length of your data may be shorter (30 minutes if the base is 10-20km far from you, 1 hour if the base is 30-50 km, etc.)…
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