Notes on how to use ArcGis
This page deals with how we specifically used ArcGis in Archaeology. We also document the following topics:
Three different implementations Vector Models (also called FeatureClasses) in ArcGIS (for now we'll assume that these are differently formatted files - not separate models)
Coverages (file based model)
ShapeFiles (file based model)
- Raster Models: Images or Grids. Of these two, images are well understood. Grids can be made from images, but in essence they allow attributes to be stored for each grid square in the picture.
TIN stands for TriangulatedIrregularNetworks.
Initial process developed to use points from a Garmin GPS
To start with you will be working in ArcMap.
Importing GPS Data
First we used a USB GPSMap 76 CS Garmin to find points. This was preliminary work while we were waiting to get the survey equipment.
To import the points we use the DNRGarmin add-in for ArcGIS. It works beautifully! Import the track as points. This will create a ShapeFile.
Use the 3dAnalystExtension to make a Surface TIN out of the shape file. Now you have the surface data you need to drape the image over.
Rectifying the Image
Assuming you have an image, you need to import and add it to the project. (By the way you may want to look at the ArcCatalog for more info on this). Once you have the image imported, use the GeoReferencing toolbar to Move the image in place by repeatedly using
- Fit to Display
- Scale
- Shift
- Rotate
Once you are about there, you can use the add control points tool to scale the image and move it into place. See the RectifyingImage.pdf tutorial for extended directions.
Finally rectify the image in the GeoReferencing toolbar. This will create another image that has spatial data attached to it.
Creating the 3D image
In ArcScene open add the TIN created above and the Image created in the previous section. Right click on the image and select properties. Select the Base Heights tab and click the radio button to Obtain heights for layer from surface. Select the TIN file if it isn't already selected and click OK. Uncheck the TIN layer to just see the picture.
IF the heights aren't very well defined you can exaggerate them by right clicking on "Scene Layers", properties, General Tab, Vertical exageration set to 2 or whatever.