You need to install Dynamo, click here
Open Revit file with topography & select Dynamo under Add-ins menu
This will open Dynamo window, hit New
We are now in Dynamo file
In search at top left corner, type select model element.
You will see the options coming up to select, select “Select Model Element”
Below tab will pop-up to select the element
Hit Select in it & select the Topography in Revit
See that after selecting element id will be shown
Now in search tab type Topography.Points & select Points shown below
Select Elements & topography, as shown
Now search Code, select Code Block
In Code Block, Type P & hit cursor outside
Now after P type .X; enter, type P.Y; enter & type P.Z;
Link above to Points in Topography
Search for string from array, link this tab to code block as shows
Now search for csv. & select WriteToFile
Below tab will appear
Link it as below
Search for file path & select the one shown below
Link it with filePath of CSV.WriteToFile
Hit the Browse tab in File Path to save the text file, remember to give separate name else files will override each other
This will give you three separate text file of points
Enjoy