NGS Leveling Adjustment Course

1. NGS Leveling Adjustment Course Module 2: Conducting leveling adjustments using NGS IDB • Course requirements: • VPN (for remote access) • UNIX emulator (e.g. PuTTY) • User profile with access to IDB and leveling menus

2. Outline • Some basic theory • Recommended file structure • Obtaining line information, R6 files and HGZ files • Editing the CONSTRAINTS file • Running Adjustment

3. Adjustment theory • Leveling adjustments are made when new leveling work is to be published with older work, specifically when • There are multiple connections to older work • New starting elevations, e.g. tide gauge, or the application of a vertical rate (VTDP) • If new work obtains starting elevations from one existing line, no adjustment is needed, as new work will be consistent with published heights

4. Adjustment theory • A goal of adjustment is to have an updated, CONSISTENT leveled network with the minimal number of changes to published values

5. New - Old = 0 cm BM Z Area of Adjustment (e.g. subsidence area) 1970Line (old) New starting height here New - Old = 5 cm BM A 2009 Line (new)

6. New - Old = 0 cm BM Z 1970Line (old) Area of Adjustment (e.g. subsidence area) Need to make sure adjustment is consistent where lines come in close proximity 2.4 cm 2.6 cm BM B New starting height here New - Old = 5 cm BM A 2009 Line (new)

7. Area of Interest (e.g. stable area) 1970Line (old) 1980 line (old) 2009 Line (new) Constrain new work to OLDER observations

8. 1. Create required file structure • Create a folder for the adjustment in UNIX • recommendation to name according to state(s) and level of adjustment (e.g. AL_Scondary) • Use UNIX command: “mkdir”<space> <name> <Enter> • Open folder with command “cd”<space> <name> • Within this folder, create “input” and “results” folders “mkdir”<space> “input” <Enter “mkdir”<space> “results” <Enter> • Verify by listing adjustment folder contents (“ls”<Enter>)

9. 2. Create a “lines” file • Within project directory, invoke the vi editor to create lines file “vi lines”<Enter> • Enter the list of line names Change to insert mode by typing “i” or <Shift>A Type line name/number; use “/” to designate parts of lines (e.g. L5969/2) and hit <Enter> key after each name • Save file In command mode, type “:wq!” or <Shift>”ZZ” to save and exit • Copy lines file to both input and results folders Use copy command “cp lines input/” and “cp lines results/”

10. 2. Create a “lines” file (cont.) • Use “retline” in menu_v to download ALL published lines within a geographic grid • menu_v • #11 • Enter geographic coordinates as prompted

11. 2. Create a “lines” file (cont.) “lines” file will have too much information: need to cut first 12 characters and place them in new file: cut –c1-12 lines > lines New file will overwrite old file All we need is first column (characters 1-12)

12. 3. Retrieve R6 files • Within the input directory (e.g. [~/AL_Secondary/input]), invoke the vertical menu Type “menu_v”<Enter> • Select option 9 (ret_vobs6) Type “9”<Enter> At the prompt, type “lines”<Enter> to indicate file name for lines Type “83”<Enter> to indicate horizontal datum Type “88”<Enter> to indicate vertical datum Add gravity (type “y”<Enter>) Use NAVD 88 grids (type “1”<Enter>) • When done, hit <Enter> then exit vertical menu (“x”)

13. Example of ret_vobs6 program for obtaining R6 files from a list of line names (“lines” file)

14. 4. Create HGZ file from R6 Line order command will convert R6 files to HGZ format Remaining within the input subdirectory, invoke command: “lnorder” (space) <R6_filename> (space) filename Example: [~/AL_Secondary/input]lnorder R6_L25606 L25606 <Enter> UNIX prompt indicating active directory New HGZ file name R6 file name For batch-running lnorder command, type: /home/vkammul/Kathyk/exedir/lnorder_multi.sh (requires you to specify first R6 file in alphanumeric order in input folder)

15. 5. Retrieve constraints • Navigate back to main project directory “cd ..” <Enter> • Invoke vertical menu “menu_v” <Enter> • Run ret_vcon script “12” <Enter> • Accept all defaults (hit <Enter>) • File name: lines • Vertical datum: 88 • Input file type: HGZ • Group option: On • Loop option: On • Tau: 0.05 • Norm: 2.50 • V: 5.00

16. 6. Manage CONSTRAINTS file • Make a copy of the original CONSTRAINTS file “cp CONSTRAINTS CONSTRAINTS.orig” <Enter> • Edit CONSTRAINTS file “vi CONSTRAINTS”<Enter> • Confirm that all level lines are included • Remove or comment out all “CONSTRAIN PID…” lines except for the ones you want to retain as constraints in your adjustment

17. 6. Manage CONSTRAINTS file (cont.) In this example, we have removed all but PID BG2513, and have retained the published value. In the vi editor, we could also change the value of the constraint to a new value from another adjustment (we’d want to then change the comment to indicate where the new/updated value was obtained).

18. 6. Manage CONSTRAINTS file (cont.) In this example, we include some constraints from primary adjustments and others from a secondary adjustment, as well as holding some published values

19. 7. Running the adjustment • Run adjustment in main project directory (“asta” command) “asta CONSTRAINTS”<Enter> • Adjustment uses CONSTRAINTS file Make sure CONSTRAINTS file has the proper PIDS constrained More complicated adjustments will specify PIDS or observations to drop, or float • Outcome of adjustment is the CONSTRAINTS.report file (found in results subdirectory) Verify that adjustment was successful by opening the CONSTRAINTS.report file If there was a problem, it should be noted by a comment in the file

20. 7. Running the adjustment (cont.) • Generate R6 report files • From the main project folder, enter vertical menu “menu_v”<Enter> • Select #10 – generate report (rpt_gen) “10”<Enter> <Enter> “x” to quit vertical menu • Verify successful outcome “cd results”<Enter> “ls”<Enter> -should see a listing of ***.rpt files