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VERTCON vs ADJUSTED elevations


Papa-Bear-NYC

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A related question to my previous post:

 

"VERTCON" is defined as on the NGS dsdata.txt as

VERTCON = The NAVD 88 height was computed by applying the VERTCON shift value to the NGVD 29 height. (Rounded to 0 decimal places.)
and here's the example they give:
BW0768 DESIGNATION - 1 BOLT

BW0768 PID - BW0768

BW0768 STATE/COUNTY- MS/ADAMS

BW0768 USGS QUAD - NATCHEZ (1976)

BW0768

BW0768 *CURRENT SURVEY CONTROL

BW0768 ___________________________________________________________________

BW0768* NAD 83(1986)- 31 33 42. (N) 091 24 25. (W) SCALED

BW0768* NAVD 88 - 59.70 (+/-2cm) 195.9 (feet) VERTCON

BW0768 ___________________________________________________________________

BW0768 GEOID HEIGHT- -26.30 (meters) GEOID03

BW0768

BW0768 VERT ORDER - FIRST CLASS II (See Below)

...

BW0768

BW0768.The NAVD 88 height was computed by applying the VERTCON shift value to

BW0768.the NGVD 29 height (displayed under SUPERSEDED SURVEY CONTROL.)

BW0768.The vertical order pertains to the NGVD 29 superseded value.

...

BW0768 SUPERSEDED SURVEY CONTROL

BW0768

BW0768 NGVD 29 (??/??/92) 59.696 (m) 195.85 (f) ADJ UNCH 1 2

When is it VERTCON and when is it ADJUSTED? What does this category imply about the vertical control prior to the VERTCON shift? Here's an old mark that was adjusted from the old value, not shifterd:

KU0982 DESIGNATION - TIDAL 737 STA II 6

KU0982 PID - KU0982

KU0982 STATE/COUNTY- NY/QUEENS

KU0982 USGS QUAD - FLUSHING (1979)

KU0982

KU0982 *CURRENT SURVEY CONTROL

KU0982 ___________________________________________________________________

KU0982* NAD 83(1986)- 40 47 41. (N) 073 46 54. (W) SCALED

KU0982* NAVD 88 - 3.004 (meters) 9.86 (feet) ADJUSTED

KU0982 ___________________________________________________________________

KU0982 GEOID HEIGHT- -31.32 (meters) GEOID03

KU0982 DYNAMIC HT - 3.003 (meters) 9.85 (feet) COMP

KU0982 MODELED GRAV- 980,257.0 (mgal) NAVD 88

KU0982

KU0982 VERT ORDER - FIRST CLASS II

KU0982

...

KU0982.The orthometric height was determined by differential leveling

KU0982.and adjusted by the National Geodetic Survey in June 1991..

KU0982

...

KU0982 SUPERSEDED SURVEY CONTROL

KU0982

KU0982 NGVD 29 (??/??/92) 3.331 (m) 10.93 (f) ADJ UNCH 1 2

 

I cannot see how the original pre-VERTCON value in the first example was controlled. They both say "ADJ UNCH" in the superceded control line.

 

Can anyone explain.

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