Re: How can I add a custom EPSG to the Map (Geometry) Viewer in PGAdmin4, - Mailing list pgadmin-support
| From | Calle Hedberg |
|---|---|
| Subject | Re: How can I add a custom EPSG to the Map (Geometry) Viewer in PGAdmin4, |
| Date | |
| Msg-id | CAPB4dVgdckCNvfNpejtP9BTBEzSpwZRog9Rty3LRi1jhHw7s9g@mail.gmail.com Whole thread Raw |
| In response to | Re: How can I add a custom EPSG to the Map (Geometry) Viewer in PGAdmin4, (Avin Kavish <avinkavish@gmail.com>) |
| Responses |
Re: How can I add a custom EPSG to the Map (Geometry) Viewer in PGAdmin4,
(Dave Page <dpage@pgadmin.org>)
|
| List | pgadmin-support |
Dave,
EPSG is a structured data set of Coordinate Reference Systems and Coordinate Transformations - the data set was originally designed by the European Petroleum Survey Group (EPSG) but is from 2005 maintained by the International Oil and Gas Association Survey Committee.
Each EPSG has a unique Spatial Reference Identifier (SRID), and as indicated above it defines both the DATUM (Coordinate Frame, or in more daily English it's a model of the Earth), the PROJECTION (or no projection), and the necessary parameters for transforming data from one EPSG to another.
The EPSG = 4326 which Avin references above is the most basic/common EPSG of all: the datum is WGS-84 (defined by the US and used in their GPS system), and it uses decimal degrees with no projection: north-south LATITUDES go from 0 degrees at the equator to 90 degrees at the North Pole and -90 degrees at the South Pole, and east-west LONGITUDES go from the 0 degree meridian (historically called the "Greenwich Meridian") to 180 degrees eastwards and -180 degrees westwards.
US datums and projections (like UTM, Universal Transverse Mercator) became dominant for global cartography after World War 2 due to the US economic and military dominance, which continued with their World Geodetic System 1984 datum (WGS-84) used for their GPS Global Navigation Satellite System (GNSS) - but that dominance is slowly fading and there are more global players in the GNSS arena:
- the Russian GLONASS GNSS uses the PZ-90 datum
- the European GALILEO GNSS uses the GTRF datum
- the Chinese BIDOU GNSS uses the CGCS2000 datum
Before these recent global datums we had several hundred local datums, based on land surveying by either military or civilian surveys (guys trekking from hilltop to hilltop using theodolites and the like).
The global datums above is always to some extent a compromise, trying to average out errors for the whole globe. Which is why countries are still creating variants of these because they want/need higher accuracy for things like cadastral mapping (land parcel ownership boundaries), where you usually require 5cm or better accuracy in urban areas to avoid too many lawyer feasts when neighbours start feuding over the fence. South Africa, for instance, have their own "Hartebeeshoek" datum that differs from WGS-84 by 20-30 centimetres only... (Geographers are funny creatures - the adrenaline rush the rest of us get from e.g. kinky sex, they get from improving geodetic accuracy by 7 millimetres...)
Now add a large number of potential projections - where the round earth surface is projected onto a flat surface - and you see why POSTGIS have over 5,000 EPSGs in its spatial reference system table.
For normal users of navigational data (smart-phones etc), it's usually relatively simple: Modern GNSS chipsets are increasingly seamlessly handling and combining the signals from all satellites (31 GPS, 24 GLONASS, 27 GALILEO, 27 BEIDOU), and they convert it into whatever EPSG/SRID the user prefer or whatever is used by their apps.
This was probably more than you wanted to know about EPSG, but you can always dump it again when your grey cell ram gets full ;-)
Best regards
Calle
On Thu, 1 Aug 2019 at 12:45, Avin Kavish <avinkavish@gmail.com> wrote:
Hey bobb,but we have a custom EPSG, where do I add this into PGAdmin4EPSGs are stored in a table called spatial_ref_sys. All you need to do is insert a record that contains the definition in well known text format and proj4 format (for transformation). I'd recommend checking the table first because there over 5000 EPSGs in it. epsg.io shoud give you an idea of what the insert statement should look like. ExampleINSERT into spatial_ref_sys (srid, auth_name, auth_srid, proj4text, srtext) values ( 4326, 'EPSG', 4326, '+proj=longlat +datum=WGS84 +no_defs ', 'GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["WGS 84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],AUTHORITY["EPSG","6326"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4326"]]')Also, it would be nice to add in our own background mapping layers as well, is there a method for adding in WMS/WFS to the layer list?Till support for custom layers land, once you have added your custom EPSG to the database you can transform the geometries to SRID 4326 and assuming they are on Earth, they will show up on the map. The following functions will be helpfulst_srid - Check the SRID of a shapest_setsrid - Change an SRID without transforming coordinatesst_transform - Transforms a geometry from one EPSG to anotherSo when you are selecting data from a different EPSG, use: select st_transform(geometry, 4326) from table_name and it will enable the world map. AFAIK no other EPSG is supported for viewing on the map without transformation. I discovered it by sheer accident.On Wed, Jul 31, 2019 at 7:54 PM Basques, Bob (CI-StPaul) <bob.basques@ci.stpaul.mn.us> wrote:All,
Following the appreciation thread and saw the reference to the geometry viewer, I didn’t even know that was in there. Anyway, nice, but we have a custom EPSG, where do I add this into PGAdmin4?
Also, it would be nice to add in our own background mapping layers as well, is there a method for adding in WMS/WFS to the layer list?
Thanks
bobb
HISP
Researcher & Technical Specialist
Health Information Systems Programme – South Africa
Cell: +47 41461011 (Norway)
Iridium SatPhone: +8816-315-19119 (usually OFF)
E-mail1: calle@hisp.org
E-mail2: calle.hedberg@gmail.com
Skype: calle_hedberg
pgadmin-support by date: