Version 2.0 February 25, 2003 
README for Topographic Model
In this directory are a series of files that represent the digital shape model of Borrelly's 
nucleus that was generated by the Geomatics Group of the USGS Astrogeology Program. 
These products were briefly described in Soderblom et al., Science, v. 296, p. 1087, May 
10, 2002. The convention used in this model is x-axis to the right (down row), y-axis up 
(up column) and z-axis toward the viewer. No smoothing has been applied to these 
models. Depending on the use it is recommended that users employ some form of 
smoothing to suppress the noise in the data set. The model is presented in three forms:

1. The first set (starting with dem_ ) contains the 3-D digital shape model is represented 
both as floating point ISIS cube files (*.cub) and in ascii text format (*.txt). Units are in 
meters. For the ISIS cubes NULL value represent off-object and non-soluble data points. 
In the ascii versions (*.txt) the NULL value is converted to –9999.

dem_x_component.cub		dem_x_component.txt
dem_y_component.cub		dem_y_component.txt
dem_z_component.cub		dem_z_component.txt

2. The second set (starting with n_ ) contains the surface normals. Again two sets are 
provided (ISIS and ascii) and again non-valid data are NULL in ISIS and –9999 in ascii.

n_x_component.cub		n_x_component.txt
n_y_component.cub		n_y_component.txt
n_z_component.cub		n_z_component.txt

3. The last file is an orthographic rectified version of the highest resolution image 
(ccd_near_1.pds); again this is a floating-point ISIS image file in I/F units.

ccd_near_1_ortho.cub