Hello
Can Someone please tell me the differences between geometric and gravimetric heights in terms of geodetic convention....
any help would be appreciative
Regards
Mat
You need to be a member of Land Surveyors United - Global Surveying Community to add thoughts!
Add Posts, Surveying Photos, Videos and Articles to the Surveyor Community
Add Stuff to Community
We are committed to allowing freedom of expression for all of our members, and that includes maintaining a safe space for people with opposing views to express themselves. We get posts from all over the country and even the globe, so needless to say, people come with different viewpoints on lad surveying practices and processes. We see this diversity and variety as a real strength-- dialogue and debate are an integral part of the educational process, as well as an important tool in exploring different sides of complex issues.
Replies
The earth is not a perfect sphere and is composed of different types of material that have different densities. As a result you can't measure "height" or "elevation" by simply measuring how far it is from the theoretical center of the earth.
In order to compensate for these facts height or elevation must be determined by using a gravity model which accounts for the differences in the composition and shape of the earth.
There is no set difference because it varies from place to place. The more accurate your gravity model is the better elevations can be determined. There are also different gravity models.
This is one of the reasons you hear about mountain heights being determined to be at a different height than previously found.
An easy way to visualize this effect I am talking about is to think about a spirit level. The bubble finds the point where it is centered in gravity. As the bubble approaches a mountain made out of iron for example it tends to lean away from the mountain because the liquid the bubble is in is being attracted toward the mountain by the gravity from it.
good answer Karl...