# Projecting 3d points to elevation model

Global Mapper UserPosts: 3
edited December 2014
Hi All,
Is that possible somehow to project some 3d points to a surface with global mapper (at a given direction, angle in the 3d space)?
Thanks.

• Global Mapper Developer Posts: 195Moderator, Trusted User
edited December 2014
It is possible to edit the points so that the elevations are clamped to ground (digitizer edit point/line/area). I'm not sure if that's what you're looking for. We can also create points a given distance and bearing from another point, but that is strictly 2D right now. If you could provide a bit more detail about what you need, perhaps we could include this in a future release.
• Global Mapper User Posts: 3
edited December 2014
HI,
I will explain a bit more. Given a 3d point in space (above or below a DEM), calculate the intersection of a line going throught that 3d point at a given azimuth and a vertical angle. Real life example: The points of that line are projected to the underlaying surface at a givel azimuth, vertical angle, so the lower blue line is 3d line on the given surface. Where to use? Landscaping, landscape development (dams, riverbeds,..)

line_slope_elevmodelmesh.jpg

Another approach is, given a central projection camera with a focal length (maybe mm), and a projective center (x,y,z, perhaps in meters, this is the simple case...) and the terrain, place this camera somewhere in 3d space and try to find its footprint on the terrain (coverage calculation, coverage borderline will depend on the relief ). It is a common task when planning flights with UAS planes or in photogrammetry and few sw is out for this.
So I think the base idea is a 3d COGO problem, used for points. I hope this helps, I'm ready to participate.
• Global Mapper Developer Posts: 195Moderator, Trusted User
edited December 2014
This may work for you:
1) Create a 2d COGO line from given point along given bearing
2) Use the 3D Path Profile/Line of Sight tool and draw a line over the one created in step 1
3) Click "Line of Sight" button
4) Enter the elevation of the end points. One will be the elevation of your given point, the other will be calculated to give desired elevation angle. Click OK.
5) Place cursor on point where LOS line intersects surface
6) Right click and select "Create Point Feature at Cursor Location"
7) Repeat as needed