Geoid model question for non US surveyors
I am going to be teaching a one day class next week on GNSS in a small country with very little survey infrastructure. They will soon be getting a network of CORS. I wonder what users in countries without a good geoid model do for transforming heights?
EGM08?
When I did work for a water system in Ecuador, it was in an area with no existing control at all, so I used EGM08 to get orthometric heights. It was a small area so I am sure it will work fine. However, when dealing with a large area, I would imagine the uncertainties and unmodeled biases in a worldwide model like EGM08 would cause problems. However, since they have no leveling network at all except along the coast, it may not matter. They certainly do not have the resources to create a leveling network or to compute their own geoid. Plus, the interior of the country is largely uninhabited jungle with few roads.
The following week I will be attending the SIRGAS 2018 symposium in Mexico, I will have plenty of opportunity to discuss this then, but unfortunately that will be AFTER the class.
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