RobertoTjesse / Lowest-Astronomical-Tide

Making use of QGIS, BLAST and POSTGRESQL to assess MSS and LAT

Obtaining a LAT model for a defined study area

In order to provide calibration geoids for subsea surveying in European waters I created this small workflow/guideline. Use with care.

Prerequisites

• GUT (GOCE User Toolbox) , find it here
• You will need PostgreSQL+PostGIS, a relational database with geometry functions to rapidly access heights, study areas and make basic calculations
• PgAdmin3 (PgAdmin 4 is still a little bit buggy) in order to manage your own database
• QGIS (>LTR)
• BLAST more info here, find a download link here

Downloads and installs

1. Download and install PostgreSQL with PostGIS , PgAdmin3 and QGIS in case you havent yet

   1. Follow this link to download PostgreSQL with PostGIS

      https://www.enterprisedb.com/software-downloads-postgres 
      

   Here you need to get EDB Postgres Standard / PostgreSQL >= 9.6

   After having chosen the right location for the program files, make sure you choose the hard drive where you want to have your database. I used an internal Solid State Drive to ease on speed. At the end of the installation you will have the possibility to install addons. Here you have the option to install PostGIS and create a sample Database. Do this.

   2. Follow this link to install PgAdmin3

      https://www.pgadmin.org/download/
      

   At the time I wrote this I wasnt being very succesful with pgAdmin4, hence I recommend pgAdmin3.

   3. Follow this link to install QGIS

      https://qgis.org/en/site/forusers/download.html
      

   The Standalone installer will do for now.

2. Follow this link to get BLAST http://blast-project.eu/media.php?file=604

3. Download GUT , find it here

Get PostgreSQL running

5. Get PostgresSQL running by opening PGAdmin3 and creating a new database.
6. Create a new database called DTU by right clicking the already existing database >New Database...
7. Click on dtu/Schemas/Tables(0). This is the place where our new tables will be listed. At the moment its empty. Go back to this step to check if you are running your steps accordingly.
8. Minimize PGadmin3, we will come back soon.

Download the altimetry based Mean Sea Surface models from the Dennish Technical University

1. Download and extract the DTU xyz files to be imported. In this script we will import DTU 15 with 2 min separation from: ftp://ftp.space.dtu.dk/pub/DTU15/2_MIN/

Transform them to Tide Free

1. Make use of GUT software to tranform the grid into Tide free.

Make a CSV with MSS (Mean Sea Surface) values

4. Mouse yourself into PgAdmin3 to dtu/Schemas/Tables(0) and run the following QUERIES to create the database.

   

5. Open QGIS, on the browser, look for the pink blue elephant and right click on it, >Add new PostGIS connection

   

   Add your username and password

6. Go to the DBase manager inside QGIS

7. Connect to your localhost and database

8. Right click on the created table and select >Add to canvas to the new study areas

9. Export as CSV in case you need to use the model

Make a CSV with LAT (Lowest Astronomical Tide) values

5. For this we will run the derived MSS file through BLAST

6. To get BLAST running you just need to decompress BLAST in your program file folder. Afterwards make sure to make a folder in your C drive entitled blastdata C:/blastdata Inhere paste 2 folders, vrf and masks. They are located in the decompressed blast folder.

7. Open your CSV file with the MSS values for your study area. Add a new column entitled Title and automatically fill it with a increasing index (for example: 1,2,3,4... or A001,A002...)

8. Export it as a tab delimited file

9. It should look like

   Title	lat	lon	newheight	country	syst
   A0001	58.25	2.8667	44.176	8	2
   A0002	58.25	2.9	44.155	8	2
   A0003	58.25	2.9333	44.13	8	2
   A0004	58.25	2.9667	44.106	8	2
   A0005	58.25	3	44.086	8	2
   A0006	58.25	3.0333	44.067	8	2
   ...
   

10. Open the file and add a # in fron of the header

11. Save the file as data_06.inp

12. Download the following folder and save it under your examples folder. In my case it is C:\ProgramFiles\BLAST_height_transformation_tool\blastrafo_release1.1\examples

13. Run the example_66.bat

6. The resulting dtu_lat.inp.out is your resulting LAT model.

7. Open it with EXCEL in order to edit the variable space between columns and save it as a flatsimple CSV.