$BEG_SKIP


OVERVIEW:

This sample file contains data for a Distance/Distance intersection problem
based on horizontal distances from two known points. 

For this example, there are two points with known geodetic latitude and
longitude (points AAA and BBB) and one unknown point (CCC provided with an
approximate latitude and longitude). From each known point (AAA and BBB),
the known horizontal distance (to CCC) has been measured or is known.

By performing a 2D geodetic network adjustment (at an average project height), 
COLUMBUS can easily determine the position of the unknown point CCC. 

In this example, we have no redundant observation data. The intersection
calculated will be the unique solution (not a least squares best fit). 
Without redundant observations, the least squares linear equations treat
the computation the same as any generic distance/distance intersection 
algorithm would. The weights (determined from the standard deviation for 
each distance observation) will have no effect on the outcome when there
are no redundant observations.



DETAILED STEPS:

1) Start COLUMBUS and load this data file (DistDist2DGeoIntersection.txt). 


   **** Options Setup:
2) Enter the Options - Units dialog box and set the Active linear units to 
   be U.S. Feet.

3) Enter the Options - Datums dialog and set the datum to be NAD 83 if it
   is not already set.

4) Enter the Options - Global Settings Tab and set the 2D Height to be 
   6000.0 feet. 


   **** Adjusted the network
5) Set the View to be 2D Geodetic.

6) Select all stations to be included in the adjustment.

7) Select station AAA and BBB to be fixed in 2D.

8) Enter the Select Observations dialog, select all observations.

9) Start the network adjustment. COLUMBUS will not be able to compute the
   approximate coordinate for station CCC, because another distance would
   need to be measured. However, we have provided an approximate coordinate,
   so simply continue with the adjustment (from the warning dialog box).
    
   The latitude and longitude of station CCC should be:

   N  44-26-46.54158
   W 105-05-34.04441
    

10) Keep the adjustment summary window open and view the results (Adjusted
    coordinates, observations, etc.)


$END_SKIP



$STATION_TYPE_FOR_OBS
  2D_GEO

$DATUM
  NAD 83
  6378137.0
  298.257222101

$UNITS
  U
  D
  1


! Station AAA and BBB have known latitude and longitude
$GEO_COMPACT; AAA; 44.2620283; 0; -105.0534081; 0; 6000.0; 0; 0; 0; 6000.0; 0; 0; 0; 0; 0
$GEO_COMPACT; BBB; 44.26468378; 0; -105.0457644; 0; 6000.0; 0; 0; 0; 6000.0; 0; 0; 0; 0; 0
! Station CCC has an approximate latitude and longitude
$GEO_COMPACT; CCC; 44.2646542; 0; -105.0534044; 0; 6000.0; 0; 0; 0; 6000.0; 0; 0; 0; 0; 0


! Observation data (horizontal distances only)
$BEAR_COMPACT; BBB; CCC; NOOBS; NOOBS; NE; 2641.60000; 0.66001
$BEAR_COMPACT; AAA; CCC; NOOBS; NOOBS; NE; 2659.95000; 0.66001