Format of the "GPS/Leveling" file
Right justified unless noted

  00 -  04   blank
  05 -  34   Designation                  (left justified)
  35 -  45   Geodetic Latitude            (DMS format:  DDMMSSsssss)
  46 -  46   Geodetic Latitude Hemisphere
  47 -  58   Geodetic Longitude           (DMS format:  DDDMMSSsssss)
  59 -  59   Geodetic Longitude Hemisphere
  60 -  60   blank
  61 -  67   Ellipsoidal Height   (mm)
  68 -  68   blank
  69 -  75   Orthometric Height   (mm)
  76 -  76   blank
  77 -  79   Elevation Code
  80 -  80   blank
  81 -  82   Horizontal Datum
  83 -  83   blank
  84 -  85   Ellipsoid Height Order/Class
  86 -  86   blank
  87 -  88   State ID
  89 -  89   blank
  90 -  95   Permanent Identifier (PID)
  96 -  96   blank
  97 - 101   Lat Sigma (cm)
 102 - 102   blank
 103 - 107   Lon Sigma (cm)
 108 - 108   blank
 109 - 119   Lat_Lon_Correlation 
 120 - 120   blank
 121 - 125   Ellipsoid Height Sigma (cm)
 126 - 129   blank
 130 - 130   Reject Flag - H, h, S, D
 131 - 134   blank
 135 - 145   Comments  (left justified)


COMMENTS


Ortho Datum Code
----------------
 Code    Explanation
 H 88   North American Vertical Datum of 1988

Reject Code
-----------
Rejection is based on three tests. The first test is to evaluate the given 
ellipsoid height errors and determine outliers. Points outside of the 95% 
confidence level (two sigma) after 4 iterations are rejected and assigned 
'h'. Points are then compared to a gravimetric geoid to form residuals. 
Points with abnormally large residual values are dropped as having a bad
orthometric height 'H'. 

h       Ellipsoid height error
H       Orthometric height error
D       Duplicate
Blank   Indicates no rejection.

Ellipsoid Order & Class (OC) Codes
----------------------------------
The OC codes are used to classify each ellipsoid height value 
observed and adjusted at horizontal control points. The first
character indicates order while the second indicates class in
accordance with the following draft standards for classifying
ellipsoid height determinations:

 OC Code   Classification       b = maximum height 
                                difference accuracy
   00    NRA2007 absolute accuracy determined instead
   11    First Order, Class I           0.5
   12    First Order, Class II          0.7
   21    Second Order, Class I          1.0
   22    Second Order, Class II         1.3
   31    Third  Order, Class I          2.0
   32    Third  Order, Class II         3.0
   41    Fourth Order, Class I          6.0
   42    Fourth Order, Class II        15.0
   51    Fifth  Order, Class I         30.0
   52    Fifth  Order, Class II        60.0

The ellipsoid height difference accuracy (b) is computed from 
a minimally constrained, correctly weighted, least squares 
adjustment by the formula:

                        b = s / sqrt(d) 

where: d = horizontal distance in kilometers between control 
           points
       s = propagated standard deviation of ellipsoid height 
           difference in millimeters between control points 
           obtained from the least squares adjustment

The following table lists the standard errors of ellipsoid height 
differences at various distances:

                              Standard Error (mm)

       DISTANCE|                    OC Code 
         (km)  |  11   12   21   22   31   32   41   42   51   52
       ________|_________________________________________________
           1   | 0.5  0.7  1.0  1.3    2    3    6   15   30   60
           5   | 1.1  1.6  2.2  2.9  4.5  6.7   13   34   67  134
          10   | 1.6  2.2  3.2  4.1  6.3  9.5   19   47   95  190
          25   | 2.5  3.5  5.0  6.5   10   15   30   75  150  300
          50   | 3.5  4.9  7.1  9.2   14   21   42  106  212  424
          75   | 4.3  6.1  8.7   11   17   26   52  130  260  520
         100   | 5.0  7.0   10   13   20   30   60  150  300  600
           
State ID                
--------
This code conforms to the standard two digit abbreviations for states
in the United States. Additionally, codes of 'DC' and 'CD' are used
to denote points located in the District of Columbia and the country
of Canada, respectively.

Permanent ID (PID)      
------------------
Most NGS control points have a Permanent IDentifier (PID) associated 
with them. A PID for a point does not change and consists of 6
alphanumeric characters with any alpha characters being upper case.
Recently acquired GPS on bench mark points used in this analysis 
that have not been assigned a PID were instead assigned an identifier
'DRUnnn', where nnn ranges between 002 and 152. 

North-South, East-West, and Vertical Accuracy
----------------------------------------------
For points in the National Readjustment of 2007, error estimates are
provided for these points. All values are given in cm. the correlation
coefficient represents the correlated signal between the N-S and E-W 
components.