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Selvarani C, 27/02/2021 10:06

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About the Auroville CSR Geomatics Studio

We are a team working on geographical and related information with an engineering and scientific approach. The concept of geomatics is explained here: https://en.wikipedia.org/wiki/Geomatics.

We develop, maintain and publish data on this web site: https://gis.auroville.org.in.

Team

Currently, the team consists of:

  • Bala
  • Giulio
  • Philippe
  • Raj
  • Ram
  • Selvarani

Collaborations

Quick report of the collaborations the Geomatics Team the areas of work.

Collaborations

Collaborations/coordination with other other groups, etc

CSR Geomatics Description of Activity / Research / Project AA AVF LB FAMC WG CSR Talam DST
Topographic Survey of Auroville City Area in coordination with L’avenir d’Auroville: Matrimandir entire compound and Residential Zone Sector 1 completed, Sector 2 half completed yes yes
Topographic Survey of specific projects area: Vibrance, Wasteless, Cultural Zone along the Crown Road, Baraka, Gardens of Unexpected
Collective wastewater treatment systems health check-up survey: 68 plants evaluated yes yes yes yes
Manual weekly monitoring of water level in selected wells on Auroville land on approximately 50 wells (number fluctuates depending on local conditions) yes yes yes
Collection of rainfall data through manual raingauges distributed to Aurovilians: data received regularly from at least 7 raingauges yes yes
Collection of weather data through automatic weather station installed at CSR: data collected every minute, stored in the database, and published online in real time yes yes yes
Collaboration with Land Board for survey of identified land boundary stones: collection of coordinates of Government boundary stones for georefering of cadastral maps yes yes
Collaboration with AV Foundation for compilation of land ownership map: geographic land records as provided by AV Foundation, protected by login access yes
Collaboration with L’avenir d’Auroville for data sharing and coordinated system set-up: organisation of geographic data for unique online platform to enhance planning processes (initial stage) yes
Collaboration with L’avenir d’Auroville and FAMC for database links: structural work on procedures for linking databases already existing with various agencies yes yes
Study of application of drone topographic survey in Auroville context: pilot test conducted on Residential Zone with outside drone survey agency yes yes yes
Study of open source software for drone topographic survey: testing of softwares like OpenDroneMap, MeshLab, CloudeCompare to evaluate work flow, processes and limitations yes yes
Surface water modelling (ongoing): research on evaluation of surface water collection potential through automatic processing of field data yes yes
Collaboration with TALAM on research on radio-transmission for automatic wells level monitoring (ongoing): evaluation of application of radio-transmitted signals for water-related monitoring and metering (selected borewells, flow meters) yes yes
Organisation of data collected in Auroville in the past (ongoing): standardisation of data in geospatial database yes
Provision for basic statistical analyses of geographic-related data (indicators/dashboard) yes yes
Publication of collected data in standardised format on web portal gis.auroville.org.in yes yes
  • AA : L'avenir d'Auroville
  • AVF : Auroville Foundation
  • LB : Auroville Land Board
  • FAMC : Auroville Funds and Assets Management Committee
  • WG : Auroville Water Group
  • CSR : Auroville Centre for Scientific Research
  • TALAM : a project under CSR
  • DST : Department of Science and Technology, Ministry of Science and Technology, New Delhi

Our workflow

Surveys

Most field surveys are executed by our team of surveyors, using advanced DGPS equipment.
Other surveyors might also be contracted.

CAD

The survey data are imported to a CAD software (Aurocad/Civil 3D).

Editing shapefiles in Autocad

FEATURES CREATION

1. Assign a CRS to the drawing (TM-AUSPOS) (MAPCSLIBRARY command)
2. Create features in CAD (Points, lines, polygons)
3. Export shapefile (a) from CAD (Output > DWG to SDF) (Convert to LL84 – 3D)

FEATURES IMPORT INTO DB

4. Create zip file of the shapefile
5. Upload into the GISAF Shapefiles Basket
6. Import the shapefile into DB
7. Delete the shapefile from Local Machine

FEATURES EDITING

8. Open the table in QGis
9. Save as a shapefile (b) in TM AUSPOS CRS
10. In CAD, open a new drawing and assign ASUPOS CRS
11. Import the shapefile (b) (MapImport) with all Object Data
12. Edit features
13. Export shapefile (a) from CAD (Output > DWG to SDF) with ONLY the id selected (Data Tab > Select Attributes > Object Data > Filename > id) (Convert to LL84 – 3D)

FEATURES IMPORT INTO DB

14. Create zip file of the shapefile
15. Upload into the GISAF Shapefiles Basket
16. Import the shapefile into DB
17. Delete the shapefile from Local Machine

QGis

Conventions

Shapefiles

We work with QGis , a widely used open source, free software for working on maps and geographical data.

Shapefile is a standard file format for mapping, that Gisaf can import. QGis can open and save shapefiles.

We have defined some simple norms about these shapefiles for integration with Gisaf.

Coordinate system

We use CRS SRID 32644.

Column (attributes)

  • All objects in a shapefile (layer) have a unique identifier named "id": numerical value.

Field (attribute) names

  • All fields are lower case (UpperCase, use: lowercase)
  • They do not contain spaces, but underscores (not this, use: but_that)
  • The field names cannot have more than 8 characters (this_is_too_long, use: this_short)

Attribute types

  • The dates are written in ISO format: YYYY-MM-DD (eg. 1968-02-25)

Fields to remove

  • Eventually, remove the fields containing the coordinates: northing, easting, elevation, latitude, longitude, area, length, etc (these might be present when the data is imported from speadsheet)

Foreign keys

We often deal with labels or categories of objects in a layer.

A common use case to explain: Alice creates a layer of stones, and wants to tag each stone with a rating: these are picked from a list of choices, like: Beautiful, Interesting, Pretty, etc.

For these kind of attribute: define a column like rating_id (something ending with _id) as a numerical value, and assign values 1, 2, 3, etc. The text is defined in another table (typically a CSV file), that looks like:

id name
1 Beautiful
2 Interesting
3 Pretty

Code

We have defined a standard set of codes, that defines the type of data. They can be found here (TODO: add link).

Add a column code_name, matching with one the code, eg. V25 for TDEF.

Surveyor

We keep a record of the people who realized the surveys (the surveyors).
The shapefiles must contain an attribute srvyr_id, which refers to this table (TODO: add link).

Accuracy

We keep a record of the accuracy of the surveys.
The shapefiles must contain an attribute accur_id, which refers to this table (TODO: add link).

Date of survey

As nothing is absolutely permanent, it's also important to keep track of the date of the surveys: the shapefiles must contain an attribute date.

Working with Gisaf

Survey data

Raw survey data are contained in CSV files, typically downloaded from surveying instruments.

See more information of the process for the survey data (including a flow diagram): Survey data

Survey data

Workflow summary

Import basket

Gisaf provides an "import basket" dedicated for raw survey data, which is generated by land survey equipment (Leica's Total Station and RTK).

These are CSV files, like:

100081,370633.969,1327742.157,51.187,,,
100083,370628.876,1327702.913,51.565,T52,,
100082,370628.729,1327720.019,51.261,T52,,
100081,370633.969,1327742.154,51.179,,,
100083,370628.876,1327702.913,51.565,T52,,
20800,370633.969,1327742.154,51.180,,,
20801,370618.795,1327713.172,52.817,E30,,
20802,370623.674,1327711.436,51.283,B35,,
20803,370619.314,1327713.407,51.383,B35,,

Each category (5th column) must be defined in the Category table (see Categories).

Organization of the raw survey data basket

The basket should be organized in a directory structure:

- Project name (these can be themselves put in a hierarchy of (sub)directories)

- Surveyor's organization

- Equipment (eg. TS, RTK)

- Survey files (eg. Our_project-Some_comment-2018-02-23.txt)

Format of the survey file names

Our_project-Some_comment-2018-02-23.txt

The date of the survey follows the ISO date standard: YYYY-MM-DD.

Import to the database

When importing raw survey data files to the database, Gisaf does 2 steps as described below.
It's worth noting that, in this process, no reprojection is done.

Feed the raw_survey table

Each point of the imported raw survey data file is inserted to the raw_survey table:

  1. Creation of a Point geometry: the raw_survey table has a geometry column for a single point (geom) with x,y and z coordinates
  2. Save the id of the original point to the orig_id column
  3. A unique id is computed from the following fields: id, project, equipment, date
  4. The project is saved in the project_id column
  5. The surveyor identification in srvyr_id
  6. The date of survey is saved in the date column
  7. The accuracy is tagged in the accur_id, according to a mapping defined in the accuracyequimentsurveyormapping table, which depends on the surveyor and equipment
  8. The category of the point

Feed the RAW_V_* tables

From the raw_survey table, each point is then copied to its respective RAW_V_ table, with basically the same information.

These tables (which should be created manually or with the admin notebook called create_tables, as of today's writing), only contain points.

The project is saved along: see below.

Import the points

For categories that define points (opposite to lines and polygons, which require line work carried over in CAD or in a GIS software, see Line work), the points can be imported automatically to their final destination: the V_* tables.

Note: in this process, the geometries are reprojected.

Auto import of the points

The points found in the RAW_V_* tables can be imported automatically, project per project, the project page of the admin interface.

Import of the line work (lines and polygons)

See Line work

The shapefiles generated manually (line work) should be put in the project's basket, and imported from it.

Categories

The categories define the types of the geographical features.

See Categories

QGis: work on shapefiles

Go to shapefiles.

Data analysis

See Data analysis

Hosting

The team is located in the CSR of Auroville.

We have setup a server for hosting the software and database. See CSR_server for technical information about the setup.

Backup and restoration of the database

See db-support

Gear

Survey equipment

See survey equipment

Weather station

See Ambient_Weather_weather_station

Plan for future

Beside living well, see plan.

Other

Links and references

links

Old docs

Shapefiles
Data (measurements, auxiliary tables)

Pavneet's docs (imported from gisaf's wiki)

Rules of Map making - What all Maps should have!
Survey Database
Field to finish
Survey Data Post-Processing
Wells Documentation
Civil 3D useful commands
Online references for Civil 3D
connections in QGIS- using browser panel and Add postGIS
Reconcilation of Raw survey data using pgAdmin
importing RAW data to GISAF
Editing Z value of features in Shapefiles in QGIS
Miscellaneous- Civil 3D
Documentation- Rain Gauge
Documentation- Wells Monitoring (Piezometer by Bala)
Documentation- Flow meter, by Bala
Documentation- DST- Vegetation Indexing
Documentation- DST- Interpolation
Documentation- DST- Survey- Office workflow
From CAD to GIS, by Giulio
QGIS- Miscellaneous

Giulio's documentation

Documentation - Reconciliation of points using Gisaf
Documentation - Status and Status Changes
Documentation - Tags retained after re-import of same geometry

Access to data

Connection to server directly from CSR

To connect to the server directly without going through Aurinoco server, the correct url is
http://gis.csr.av

Connection to Gisaf via QGis through WFS / OGC API

This works only on QGis from version 3.14.15 onward

In the browser, click on WFS/OGC API, then right-click to create a new connection
Give a name (e.g. OGC API Qgis Gisaf)
Give the url https://gis.auroville.org.in/ogcapi

Under the WFS Options box, on Version dropdown, the default option "Maximum" works just fine
Click on OK
The list of layers will appear in the Browser under WFS/OGC API.

How to create a new projection in QGis

To create a new projection in QGis, go to menu "Settings", and click on "Custom Projections".
A pop-up window appears with a list of all projections defined in QGis projects used by the user so far.
Click on the green "+" sign on the right top part of the window to create a new projection.
In the "Name" box, type "TM CSRAUSPOS SF1" (which means TM = Transverse Mercator projection; CSRAUSPOS = theparameters for this projection are derived from the processing of DGPS raw data by AUSPOS -  Online GPS Processing Service - https://www.ga.gov.au/scientific-topics/positioning-navigation/geodesy/auspos; SF1 = Scale Factor is 1).
In the "Format" dropdown list, select "Proj String (legacy - Not Recommended)"
In the "Parameters" box, paste the following "+proj=tmerc +lat_0=12.01605433+lon_0=79.80998934 +k=1 +x_0=370455.630 +y_0=1328608.994 +ellps=WGS84+towgs84=0,0,0,0,0,0,0 +units=m +no_defs".

Finally, click on OK.

In a more explicit  way, the parameters mean the following:
Map Projection:        TransverseMercator (TM)
False Easting:          370455.6300
False Northing:        1328608.9940
Latitude of Origin:    12°00'57.79560" (DMS)  12.01605433 (DD)
Central Meridian:     79°48'35.96164"  (DMS)   79.80998934 (DD)
Scale Factor:             1.00000000
Zone Width:              6.0°

Elimination of Duplicate points – General criteria

It might happen that the same physical feature (e.g. a tree, or a pole) is surveyed more than once: this can happen because there are many physical features in an area, and the survey needs more than one station. So, for example a tree is surveyed from a station, and gets a serial number on that date. When the station is then changed, it might happen that the same tree is resurveyed: another serial number is given, and possibly a different date, if the survey from the second station happened on a different day.
It is clear that the same tree is then represented with two different points, which means that two different trees exist: but only one tree really exist in the physical reality.
It is clear that one of the two points is redundant and needs to be removed. If this is noted by the surveyor directly in the field, then the issue is solved by the surveyor himself during processing time.
If instead, due to various reasons, it was not noted by the surveyor in the field, it will need to be cleaned after the processing, possibly by post-processing staff.
How to identify duplicate points?
The following criteria can be used:
1. The distance between the two points is less than 30 cm (trees are surveyed if their trunk diameter is at least about 20 cm, so in 30 cm cannot exist two of them)
2. The orig_id (serial number) of the points are not in series
3. The survey date is not the same
4. In case of trees, the species of trees is the same
5. 5. In case of trees, the tree type is not TDEF (because TDEF are mapped irrespective of their diameter, so they can actually have a small trunk, and two of them might exist in 30 cm), not OT (many TDEF species are surveyed as OT if not otherwise indicated by a botanist)
6. The context needs to be evaluated: if one tree is deleted in an area where many trees exist in a limited space, then loosing one in the map is not a big error. If instead one tree is deleted where there are very few trees, then it might be a big loss.

Linework for the Survey Area

1. Creation of Initial Linework in QGIS using Survey points import - (Ram, System 4)

Initial Linework in QGIS is started by surveyor with the knowledge from the Field. For this step, points are simply imported into the QGIS from the field text file (.csv or .txt). CRS needs to be TM-AUSPOS. The box of “First record has field names” shall not be ticked. In Point Coordinates, select the correct field for x, for y and for z (usually “field_2” for x, “field_3” for y and “field_4” for z). Points can be styled using the “Categorized” style in “Symbology”, using “Field_5” as value, or using a Rule-based symbology using the category (field 5) as filter.
Linework is created by connecting points having same description and belonging to the same physical feature. All line and polygon features are created as lines.
The Initial Linework for the Survey Area is also stored temporarily in

D: > AVSM > Zone-Survey number (eg RZ-01) > Survey Area (eg J) > Temporary WD

Note: The line shapefiles / Geopackages shall be in CRS: TM AUSPOS

2. Creation of final working drawing Shapefiles / Geopackages - (Selvarani, System 1)

Final working drawing Shapefiles / Geopackages are created from the Initial Linework of Survey Area.
As the Surveyor draws all features as lines (both for lines and polygons features), the following actions shall be done:
1. If features are lines:
• Export the shapefile / geopackage into the final working drawing folder (Final WD), in separate folders according to its type (e.g. BLDG, FENC, ROAD, etc).

The CRS for the export shall be EPSG:4326 - WGS 84

2. If features are polygons:
• Lines shall be converted into polygons:

to do it, first click on the layer to be converted to make it active (e.g. WD-CZ-01-F-LL84_V-BLDG-MHOL------E), then go to “Vector” Menu, click on Geometry Tools, click on Line to Polygons:

The new window for “Lines to Polygons” conversion will appear:

• Always cross check the input layer, to make sure that the input layer is the active one
• Save the output in a temporary layer
• The temporary layer will be listed in the list of layers, it shall be exported to the saving location as D: > Survey > Zone-Survey Number > Final WD > Survey Area SHP (eg . D: > Survey > GB-01 > Final WD > A-Shp)

The CRS for the export shall be EPSG:4326 - WGS 84

Once all the shapefiles / geopackages are exported in Final WD, for each of the newly exported layers the Topology Checker Tool shall be used.

Linework for the whole Survey Zone

1. Merging Shapefiles / Geopackages - (Selvarani, System 1)

A copy of the Zone Master shapefiles / geopackages are taken from System 4 and stored in Temp Folder on Desktop in System 1.
Master shapefiles / geopackages are merged with the Survey Area shapefiles / geopackages:
• To do it, go to “Vector” Menu, click on Geoprocessing Tools, then click on Union:

The new window for “Union” will appear:

• To make sure that the right geometry is generated by this process (“line” type, not “Multiline”, and similarly “Polygon” type, not “Multipolygon), we need to always keep the Master shapefile (e.g. Final-CZ-01-2021-02-05-LL84_V-BLDG-MHOL------E) as Input layer, and the Survey Area shapefile as Overlay Layer (e.g. WD-CZ-01-F-LL84_V-BLDG-MHOL------E).
• (The output can be saved to a file, as the CRS should already be EPSG4326 – WGS84.)

2. Storing Shapefiles / Geopackages - (Selvarani, System 1)

Save the merged shape file in the correct location in Final folder as D: > Survey > Zone-Survey Number > Final (eg . D: > Survey > GB-01 > Final)
Date in the name of Final Shapefile / Geopackage needs to be updated.
Once the merging operation is completed, the copy of Master shapefile / geopackage is deleted from the Temp folder.

3. Topology check of merged shapefiles

The topology checker is applied again on the merged shapefiles / geopackages.
The “id_field” shall be removed from the attribute table.

4. Archive and replace the Master Shapefiles / Geopackages (Ram, System 4)

Archive the previous master shapefiles / geopackages on system 4, and copy the new merged shapefiles / geopackages in its place.
*Then delete the Merged Shapefile / Geopackage folder from System 1. *

5. Note about Shapefiles and Geopackages

All the above works are usually done using shapefile format, in QGIS latest version (3.16.3).
The Geopackage export is done in QGis versions older than 3.12 (e.g. 3.4, 3.6, 3.8, 3.10) so that the lines are not saved as “Multilines” but as “Lines”and polygons are not saved as “Multipolygons” but as “Polygons”. This is very important to be notes, as Gisaf database does not accept the Multipolygon and Multiline geometry types.