User's Guide

MAPPTS

Map ground control point collection function

Function:

A ground control point collection module which creates a tie point selection file consisting of latitude, longitude or user-defined coordinates (x,y) from a map. Input is through a digitizer or manually through the user's terminal.

Parameters:

INTS(--)
Input tie point selection file. This parameter has a value only when points are being added to an existing tie point selection file. All records in INTS are copied to OUTTS. INTS will not be changed.

INLT(--)
Labeled table file. This file contains map identifiers and parameters in a labeled table format. The file contains a map id, the latitude/longitude of the upper-left corner, lower-right corner, a verify point, as well as other information needed to register the map. If this parameter is NULL, the information is prompted for each time the map is registered. The format of the file is given in the User Notes section.

OUTTS
Output tie point selection file. The file to which map coordinates are written.

PNTFLG(NO)
Point flag. Specifies whether or not the point id will be entered by the user for each control point or automatically generated. If automatically generated, the point ids will be pt_1, pt_2, etc. Regardless of the prompting mode, point ids are not case sensitive, but must be unique.
  = YES:  Prompt for point ids.
  = NO:   Do not prompt for point ids.
ELEVFLG(NO)
Elevation flag. Specifies whether or not the elevation of each control point is entered by the user or set to zero.
  = YES:  Prompt for elevations. 
  = NO:   Do not prompt for elevations (set to zero).

Examples:

LAS> mappts outts=map.tps
In this example, a map is registered to the digitizer and control points collected are written to MAP.TPS. Map parameters are not stored in a file, point id's are not user entered, and elevations are set to zero. This mode of operation requires very little user interaction.
LAS> mappts ints=ref.tps inlt=mapid outts=map.tps pntflg=yes elevflg=yes
The header information and control point records in REF.TPS are copied to MAP.TPS. As each map is registered, its parameters and map id are written to MAPID. During the point selection process, the user is prompted for the point id, the elevation of the point, and the unit of measure of the elevation (feet or meters). Each control point is written to MAP.TPS.

Description/Algorithm:

MAPPTS is run when the user wishes to collect ground control points from a map or maps without a displayed image present. MAPPTS cannot be run in batch. First, user-entered parameters are read. If an input tie point selection file was entered, the header record and all points contained in the file are copied to the output file.
Next, the map is registered to the digitizer. This proceeds as follows:
   o  The user is prompted for a map identifier.

   o  If the labeled table of map parameters was given, the file 
      is searched for the entered map id.  If the map id is not 
      found, map parameters are prompted for.  After all user input 
      is complete, the parameters are listed and the user is given 
      a chance to edit them.  Once the parameters are satisfactory, 
      they are written to the map parameter file.  Map parameters 
      may not be changed after they have been written to the file.  
      If found, the map parameters are displayed and the user is 
      asked if they are satisfactory.  This process repeats until a 
      satisfactory set of parameters has been found or entered.

   o  The user sparks points to register the map to the digitizer.  
      By default four points are sparked.  However, up to 25 points 
      may be used.  The number of points is user defined and may be 
      increased if the map registration is not accurate enough.  The 
      user also sparks one verify point.  This verify point is not 
      used in the calculation of the fit between digitizer 
      coordi- nates and map coordinates.  It serves as an added 
      level of verification of registration accuracy.

   o  After the initial registration is completed, map coordinates,
      calculated map coordinates, and residuals (in seconds) are 
      listed.  The user may then respark any point, allowing a 
      refinement of the digitizer-to-map fit.
The user is now in point collection mode. As each point is sparked, the coordinate of the selected point is displayed. If PNTFLG=YES, the user is prompted for a point identifier; otherwise, a unique identifier is created. Likewise, if ELEVFLG=YES, the elevation of the point and its unit of measure is prompted for; otherwise, the elevation is given a zero value. The point is then written to the output tie point selection file.
At the time of point selection, the user is given the option to register a new map or exit the function.

Nonfatal Error Message:

[mappts-quit] Program aborted by user
MAPPTS was aborted by the user during map registration before any tie points were written to the output tie point selection file.

Fatal Error Message:

[mappts-fatal] Fatal error encountered
The error message displayed immediately preceding this message is the specific error encountered. Processing is terminated.

User Notes:

The user may by-pass the digitizer interface by specifying "manual" at the map-type prompt. This special map-type allows the user to enter coordinates from the terminal. Care must be taken, however, so that coordinate units are consistent from point to point in the output tie point selection file.
In cases were the latitude, longitude information is either absent from the map or is not useable, the user may define the map in terms of user-defined coordinates (x,y)--a projection grid or similar. Care must be taken in this case so that user-defined coordinates are not mixed with geographic coordinates in the tie point selection file. The user must also be certain when using multiple maps that coordinate systems are common between maps. For example, if UTM coordinates are being used, care must be taken that all coordinates in a tie point selection file are from the same UTM zone.

The map identifier file contains information needed to register a map to a digitizer. The file is in labeled table format. It may contain as many records as needed to define multiple maps used in a project. The format of the file follows:

    ;
    "MAPFILE","Map identifier parameter file";
    "ID","C","Unique map identifier",1,20
    "UNITS","I4","Coordinate unit code 4=deg 6=xy",1,1
    "UL_Y","R8","Upper left Y/latitude coordinate",1,1
    "UL_X","R8","Upper left X/longitude coordinate",1,1
    "LR_Y","R8","Lower right Y/latitude coordinate",1,1
    "LR_X","R8","Lower right X/longitude coordinate",1,1
    "VER_Y","R8","Verify pt Y/latitude coordinate",1,1
    "VER_X","R8","Verify pt X/longitude coordinate",1,1
    "NPTS_Y","I4","Number of tics in Y",1,1
    "NPTS_X","I4","Number of tics in X",1,1
    "SCALE","I4","Map scale in 1:x",1,1
    "DATUM","C","Map datum",1,80
    "TYPE","C","Map type",1,80
    "DATE","C","Map date",1,10
    "DESC","C","Map description",1,80;

Refer to the Geometric Manipulation Package Overview Document (GEOMPOD) for more information on map registration and details of the digitizer interface.