How to Begin 3D Landscape Measure/Mapping Project

I am new to Arduino, but it seems like a good place for my imagination. My parents own a farm with a very large yard with many buildings, trees, fences, ditches/waterways. I have experience with Google Sketchup 8 and I want to create a model encompassing all the terrain and buildings in the yard. The yard itself is roughly 400ft by 800 feet. Accuracy is probably only important to about and inch or two.

I have a few different ideas and I can't find anything that seems like it is ment for this besides extremly expensive 3D laser scanners for engineering purpose. The simple 3D scanners using two cameras do not have the range but the "point map" created seems like the right direction for my project. ??Is there a simple way to import one of these point maps into Google Sketchup free version??

First Idea: Altimeter watch and laser tape measure. Upon reading numerous reviews most handheld altimeters will not show small changes in altitude. I need accuracy to the inch and these are roughly accurate to +/- 10ft. The laser tape measures on Ebay can give me referance measurements so I can track my location between buildings and then I can set a grid and if Ardiuno altimeters are accurate enough I can enter all the data by hand and plot all the points. I also may be able to do this with a transit level but then i need two people. ?? How accurate are the barometric altimiters?? Could I accuretly move it only a few inches and be able to record the readings??

I know there are GPS sheilds for Arduino but they say accurate to a few meters... That to me translates to +/- 10ft. I have almost no experience with GPS but maybe someone here does. If I take a GPS reading that +/- 10ft accuracy is saying that I am within 10ft of that exact lattitude and longitude on the Earth. ??My exacty lat. and long. isn't important to me so much as if the move the GPS 2ft. is it going to be able to measure that?? Also do any GPS sheilds have allitude information??

Final Idea: Is there a way I could create a data loging system that employs a simple staff that I would walk through the yard with in streight lines and every 6 inches to two feet and log the locaton and altiude. What I thought was setting a square perimiter blasing sonar waves out and the stick sends out a wave. The different sonars could triangulate the staffs 3D position. As I walk every place I set the staff logs then that data should graph into a 3D accurate model. Is this way too much for an Arduino?

Also thought of setting a laser tape measure on a spinning rod to make a circle of height measurement from a single altitude. Then raise up the rod by one foot, spin 360 while recording the distance to create a graphable rise/run 3D model. Is there a sensor that will measure up to 50 ft like the cheap laster tapes on Ebay?? I know it would be easy enough to spin the sensor but I need a powerful enough sound sensor that interfaces with the Arduino.

I hope my misspellings and rambles are not too stupid to be understood. Any help would be appriciated. If all else fails there is an old transit level and that method has worked for this for over 1000 years. Thanks to all.

This is not my field and someone may correct me, but I can see no way to get inch resolution in altitude, maybe using your staff with an adjustable retro reflector but that wouldn't automatically get the reading unless you also use an encoder on the reflector or something, detect the laser pulse and transmit the current reflector height back to the Arduino.

I think this is a bridge too far but am very interested in the answer if it's not.

EDIT: Leave the reflector in one position on the pole and scan both H and V dimensions, when you find it use the distance and angle to calc what you need. However I think this is a very complex idea, not the trig involved but the mechanical aspects of scanning a laser with any real accuracy and pulsing the laser to measure the distance. An Arduino cannot do this by itself.


Rob

tjdux: The simple 3D scanners using two cameras do not have the range

If it's using a stereographic approach it ought to scale up, though, if you increased the distance between the cameras. I'm not familiar with the 'simple 3D scanners' you refer to but the approach which seems most promising to me would be to take several pictures from different (known) positions and use image correlation to identify common points on different pictures - from there, it would only require some simple trig to calculate the position of that point in 3D. I expect the image correlation would be quite difficult but it's the sort of problem that people tackle using OpenCV; if all else failed, you could just manually nominate corresponding points on the different images and from there the trig calculations would just be a matter of number crunching.

How you would use that mass of points to construct a Sketchup model beats me, though.

Could you modify one of those rotary laser levels? I have seen those used in landscaping before, and they are accurate to fractions of an inch. If building your own laser detector is too complicated, you could modify one of the handheld units that are designed to work with the level.