GIS

h1. %{color:BLUE}  Wiki%

h1. [[CSR Geomatics Team]]

h1. [[Collaborations]]

h1. [[Data Analysis]]

h1. [[CSR Geomatics Server Setup]]

h1. [[Database Backup and Restoration]]

h1. [[CAD to GIS Workflow]] %{color:RED}  - TO BE UPDATED%

h1. [[GIS Conventions]]

h1. [[Working with Gisaf]]

h1. [[Gisaf Workflow]]

h1. [[GIS to CAD Workflow]] %{color:RED}  - TO BE UPDATED%

h1. [[Weather Station]]

h1. [[GDAL - Useful Tips]]

h1. [[Gisaf - Auxiliary Data (non-geographical data)]]

h1. [[QGis - Useful Tips]]

h1. [[AutoCAD Civil 3D - Useful Tips]]

h1. [[Wells documentation]]

h1. [[Gisaf Data Modifications]]

h1. [[Other Useful Softwares]]

h1. *Reconcilation of Raw survey data using pgAdmin*

+For changing the layer codes, to be done using Pgadmin.+

h3.  Enter Schema> AVSM RAW Survey > Tables > select the table> Right click - View edit data > All rows. Apply filter to the original id and note the Database id's to be reconciled.

h3.  GISAf Admin> Other > Reconciliation. Create > Add the database (point) id and give the new target corresponding to the database id to be changed. (Use the Layer name in target not Raw layer name).

h3.  Other > Project > select the project > with selected> reconcile RAW survey points.

h1. Importing point data (TS and RTK) to GISAF 

# *Gisaf Admin > Basket > Survey data > "Project" > "surveyor" > TS/ RTK > upload > import.*

# *Auto import of Raw points data* (changes from Raw to Shapefiles, the point files)

  In GISAF Admin > Other> Project > select the project for which you want to import the data > with selected > Auto import to GIS...

h1. Editing Z value of features in Shapefiles in QGIS

h2. using vertex editor tool - https://www.youtube.com/watch?v=8V8i1AtcA74&t=256s

h1. Miscellaneous- Civil 3D

*Autodesk civil 3D Geotechnical module- for borehole data :- To analyse borehole data, To make profiles and calculate volumes*

https://www.youtube.com/watch?v=0Be9kShBou0

Reference videos

Exploring:

https://www.youtube.com/watch?v=gr-ISPzLcU0

Modelling:

https://www.youtube.com/watch?v=Pz0-HOoiBrs

solids

https://www.youtube.com/watch?v=mQ0Yeh6tZA8

https://www.youtube.com/watch?v=4eMsUiYBhuE

*CIVIL 3D Survey*

Getting started- Always open a new drawing with a template. 

*Description key sets*- (till 18:30) https://www.youtube.com/watch?v=mmwkkRyBkS0

As when the points come into the drawing, they are going to be filtered with description key sets and the description key sets will assign properties to the points.

Tool space > settings > points > description key sets

“Description key sets name”> edit key- to view the points in a list: 

Automatic linework (18:30- till end)

Survey > Linework code sets- for automatic linework

*Using Master view*

Uses-

copy styles from one drawing to other

copy drawing data from one drawing to other (data referencing)

*Civil 3d surface model*- from points- break lines

https://www.youtube.com/watch?v=wC40rdmDEMo

moving for example- point groups under point groups- 

*Civil 3D Planning and Analysis*

Workspace: Planning and Analysis

1. Working with Object data (GIS Attributes)

Map Setup> Define object data> New table> Define new object data table start defining fields

h1. Documentation- Rain Gauge

h2. Manual Rain Gauge

*Why it is important to comply to standards?*

1. Consistency for comparing rainfall data in different places within Auroville since rainfall varies in different parts of Auroville.

2. Making it possible to use for any kind of scientific analysis by contribution to the primary data in sustainable water management for Auroville. 

*Proposed standards and ethics:*

1. The time of taking the reading - 08:30 am. 

The rain is recorded over a period of 24 hours- 8:30 of previous day till 8:30 of the present day, and the date is put as the present day. For example, if the rain is measured at 8:30 am on 10 dec 2017, then it is logged in as on 10 dec 2017.

2. Manual rain gauge typically used- green cylindrical and a collection jar.  

3. Measuring jar: 10 mm corresponding jar

Area of the rim of manual rain gauge= 200 square cm

Diameter of rim= approximately 16 cm

*NOTE:* - If another kind of rain gauge is used, it should be used with the corresponding measuring jar as type of jar and calibration on jar depends on the area of rim. Any cases of different rain gauge other than above should be reported before use for recording purposes.

4. The minimum record-able unit is 0.2 mm (Least measure on the 10 mm cylinder). T is marked for below 1 mm.

5. The reading should be preferably submitted in an excel sheet (the data sheet will be provided). The frequency of sending data can be daily or weekly.

6. The rain gauge should be kept in a safe and open to sky area clear from tree cover or objects in surrounding so that direct rain falls into it and not from trees/ objects etc. Preferably roof top or a higher place on ground.

7. A check on the rain gauge should be kept when there is long period of gap in rainy days to make sure it was emptied out and there is no blockage. 

8. In case of doubt in reading or incorrect measure, "incorrect measure" should be marked

*Ethics*

1. Readings should not be missed. Time to time check on rain gauge is required during long periods of no rain (especially when the rain season is approaching). 

This is important because firstly, if it rained in the night and it wasn’t recorded, reading for the day is lost; Secondly, if the jar was not emptied, it gives incorrect subsequent reading. 

2.  If the person is not going to be available temporarily where the rain gauge is kept, the responsibility should be passed on to someone they can rely on after explaining the standards. 

*Important-*

Data won’t be published in case of non-compliance to standards. This is to maintain the sanctity of proper scientific data collection and to keep it reliable for sharing by publishing. Discussions regarding standards are welcomed.

CSR Geomatics Team is placed on first floor in CSR, Auroshilpam.

*AV rain data publication*: (http://gis.auroville.org.in/measures/raingauge_av).

Adding Rain gauge to our web portal (GISAF), following information is needed:

1. GPS co-ordinates of location of placing the rain gauge (can be obtained using mobile phones easily)

2. Name, place of residence & contact number- Mobile & Landline

h2. Automatic Rain Gauge

There is a possibility of publishing rain data coming from Automatic rain gauges like (id 15, auro orchard) and Weather stations. 

For Automatic rain gauges, we can upload the files coming from the rain gauge directly into GISAF.

_Thank you for contribution towards a sustainable management of Water in Auroville through Data collection._

h1. Documentation- Wells Monitoring (Manual and Automatic / Piezometer by Bala)

h2. Manual- Using tape with a sensor

Timings: The person assigned the job of monitoring collects the readings in three slots.

1.	Between 6 am to 7 am till about 9 am to 10 am.

2.	Between 11 am and 1 pm

3.	Between 2 pm and 5 pm

Things required:

•	Notebook

•	Pen

•	Measuring tape

•	Vehicle for movement

*Ethics*- 

•	The monitoring should happen in coordination with the community members/ care taker (assigned by the person in charge from within the community). There should be a clear communication from monitor side as to which days the monitoring of a well has to happen and at around what time so that it can be made sure that the pump is not turned on before monitoring. In case a pump was turned on in a well, the monitor should have a gap of about 5 hours on the same day before going again for monitoring.

•	The monitor should have contact numbers of the person in charge/ care taker for any communication.

•	If the monitoring is stopped for any reason at any point, the monitor should communicate the same to the person concerned.

•	The monitor shall take responsibility to inform any kind of changes in a well in terms of its functioning etc.

•	The monitor should report to the CSR Geomatics Team who has responsibility to publish data.

•	The monitor published the data to the website and works with the geomatics team.

*Definitions*:

A master file is maintained with the records of the wells from the field. It is updated when a new well is located. The following set of information are filled out in the Masterfile. 

*Well type*

1.	Open

2.	Borewell

3.	Dug cum borewell

*Well status*

1.	In use

2.	Not in use

3.	Closed

*Pump Status*

1.	Functioning

2.	Not functioning

*Pump Automation*

1.	Manual 

2.	Automatic

* Non-accessibility factors*

1.	Dogs

2.	Heavy slab

3.	Narrow casing

4.	enclosed/locked

5.	permission

*Data Matching Accuracy (reconnecting with harvest wells data)*

1.	High

2.	Medium

3.	Low

*Well coordinates*

For a new well, coordinates of the well position are taken on a mobile GPS.

Person In charge

For communication purpose, contact the person in charge as recorded in directory.

h2. Automatic- Piezometer (by bala, to be edited) 

The calibrations and setting are already done by Azha

The piezometer is taken to the site of unused well. First the depth and Water level  is checked manually using water meter

Then the sensor of the piezometer is inserted into the well 1m above the bottom of the well, so the sensor does not get affected from mud or water inside

The sensor sends the data to an electronic board which translates the signal into the proper output, and then it sends the signal to the transmitting device above, on the ground surface. The transmitter then sends it to the receiver at CSR, the signal is then routed to Talam office through Interneet, enters the software and the reading is processed.

The piezometer sometimes does not have proper signal and so it would not be able to send it

h1. Documentation- Flow meter by Bala

Flow meter – for checking the flow of water in pipe

CSR bought ultrasonic flow meter from Chennai and the company (company name? )trained Bala and Vijai(CSR) on how to set it up.

we tested in the west water system pump in csr. then we test in many more place .

 ami, aurodam and buddha garden borewell pumps . we got request from the water service 

Cross check they flow meters .

 so before that  we want to know how our meter works. 

so we tested in our tank . the pump pumping from our sump tank so the flow will be stranded.  when you pump in the bore well  the flow goes up and down. 

we tested two times in  15 minutes.and one time 30 minutes,so we got variation between this three. 

we find 1,5 % error but the flow meret they said  1 % error only.

we cross checked the flow meter of the water service we find some error  in they meter also. 

we tried they bore well flowmeter and they sump tank flow meter also.and we find some error also in they meters.  

then we find some error in (AVWS) meter also.

It is used to check the flow of water in pipe

tools used 

First the outer diameter of the pipe has to be entered in the device. It is measured using Vernier caliper

Then the thickness of the pipe is set which is also measured using vernier

Also the device asks for the material of the pipe. If the pipe material is know it can be set and if it not know then there is an option which is other (mostly PVC, HDPE, and  iron) 

After entering these details the device gives the spacing for the sensors. There are 2 sensors up and down which has to be fixed accordingly

When the sensors are fixed the motor is turned on and the sensors send reading to the display device

This is noted down once every minute and taken for 15 to 30 minutes. Then the average of this is determined. This is done because of the variation in the flow. This gives the flow rate in 1 hour.

This was done in different places to check to flow rate

h1. Documentation- DST- Vegetation Indexing

h2. Steps for Dzetsaka Classification tool for Vegetation indexing in QGIS

 1. Install the plugin Dzetsaka classfication tool.

 2. Open the Raster from the Survey.

 3. Create a polygon shapefile for index sampling. Mark polygons and give the ID's (1,2,3 for Tree, grass, bare land etc) Cover the variations in samples as much as possible. 

     More the samples, better the indexing.

 4. Apply Dzetsaka Classification tool, Select the base raster and the sample- index polygon shapefile created in step 3.

 5. The result is a Raster with DN numbers specified in the Shapefile in step 3.

 6. Apply the Sieve raster command (Raster> Analysis> Sieve)- Try different threshold numbers and view the results till the noise is removed from the Raster.

 7. Polygonise the Raster to Vector (From processing)

 8. Run the v.generalise tool on the shapefile. This tool removes the pixelated boundaries of the polygons in the Vector.

h1. Documentation- DST- Interpolation (Processing toolbox)

The following 4 tools have been mostly explored and the results were compared. The ones used for quick analysis are 1. Cubic Spline and 2. V.surf.spline . The rest of the tools are for further exploration and used depending on the need of the project. In some tools, the elevation values of points should be stored in the attribute table (Using field calculator and giving command - *Z($Geometry)* )

# Interpolate (Cubic spline) - SAGA

# V.surf.bspline - GRASS. Parameters to set - cell size. Set this parameter above 0.001 ( 0.00001, 0.000001 etc) and check the results.

# V.surf.rst - GRASS

# Krigging - SAGA

[[Documentation- DST- Survey- Office workflow]]  - *%{color:RED} to be written%*

h1. From CAD to GIS by Giulio

*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 FIRST TIME*

4.	Create zip file of the shapefile

5.	Upload into the GISAF Shapefiles Basket

6.	Import the shapefile into DB

7.	Save the shapefile on Local Machine

*FEATURES IMPORT INTO DB EVERYTIME*

8.	Combine the new features to corresponding last shape files (Insert the process here).

9.	Follow step 4-8 again

*FEATURES EDITING IN QGIS*

10.	Open the table in QGis

11.	Save as a shapefile (b) in TM AUSPOS CRS

12.	In CAD, open a new drawing and assign AUSPOS CRS

13.	Import the shapefile (b) (MapImport) with Object Data (Data tab > Create Object Data > OK), tick “Import polygons as closed polylines”, then press OK

14.	Edit features

15.	Change workspace into “Planning and analysis”

16.	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*

17.	Create zip file of the shapefile

18.	Upload into the GISAF Shapefiles Basket

19.	Import the shapefile into DB

20.	Delete the shapefile from Local Machine

h1. QGIS- Miscellaneous

*QGIS Introduction:*

https://www.birdseyeviewgis.com/blog/2018/2/22/my-favorite-features-of-qgis-30to-date

3D visualization of raster DEM- https://www.youtube.com/watch?v=2KrCsbP0kUs

*Spatial query:* 

Spatial Query is selection of features that satisfies a certain condition which relates to other features in a space.

Using plugin- Spatial query

http://www.geodose.com/2018/03/spatial-query-in-qgis-3.html

Labelling:

Labelling with more than one field names and in different lines

|| '\n' ||

*Hierarchy of extensions*

File levels and their uses.

https://nathanw.net/2014/03/22/all-the-q-files/

+The Project file (.qgs)+

It contains: Layer source pointer + Style information + Composers + a whole heap of other stuff

+The Layer Definition file (.qlr)+

It contains: Layer source pointer + Style information

+The QML file (.qml)+

It contains: Style information

h2. Giulio's documentation

h1. Documentation - Reconciliation of points using Gisaf

Reconciliation of points is a procedure used when a point is stored in a wrong table, because its category was either wrongly recorded in the field by the surveyor, or it has ben reviewed later by the surveyor or the data validator and found to be wrong.

h2. Definition: Raw points are all points coming from the field survey. Raw points can be points referring to a Point feature (e.g. trees, or elevation points, or floor level), or points measured in the field to draw a line (e.g. the vertices of a fence) or a polygon (e.g. the corners of a building outline).

In the overall workflow, *+reconciliation affects only raw points+*. It takes place after the field textfile is uploaded into the basket and its points imported (raw points stored in the raw survey tables). Here you can visualize the Workflow diagram: [[Survey_data]].

If a raw point refers to a point feature, reconciling it means moving it to another category/table meant for point features, not for lines/polygons. So, *+only raw points of point features can be reconciled+*. Raw points pertaining to line features and/or polygon features cannot be reconciled, so these raw points will remain in their original wrong table.

PLEASE NOTE: 

The attributes of a line/polygon, which are derived from their defining raw points, will not be modified by any reconciliation, because *+only raw points of point features can be reconciled+*.

h2. How to perform Reconciliation

To perform reconciliation of points: Login to Gisaf -> click on the G icon on the upper-left corner of the website page -> Manage -> Reconciliation by orig.ID

On the right end side of the screen, clicking on the field "Destination" a list of all categories will appear: these categories refer not to the Raw survey tables, but to the V_ tables of the database (points, lines, polygons).

Under it, in the field "Original ID", the original point number of the point to be reconciled is to be entered.

Clicking on the "Search points" button, the result shows the database unique id of the point, its survey category, its survey date, its geometry type (point, line, polygon), and the Project the point belongs to. In case of multiple points with the same original id (in case of different Projects, the field number of points might be not unique if the numbering of points in the field has restarted) all points having that original id are displayed: thanks to their date or Project or type, it is easy to identify the correct point to be reconciled.

Once the point to be reconciled is identified, clicking on the button "Reconcile" will run the reconciliation, and a message will appear stating that it has been done successfully. An error message can appear if a reconciliation of a raw point of a line/polygon feature has been attempted: this type of points cannot in fact be reconciled.

Once a raw point has been reconciled, *+it cannot be reconciled again+*. In case a raw point has been wrongly reconciled, it cannot be reconciled again through the above procedure, but it has to be reconciled manually through QGis or pgadmin software.

h1. Documentation - Status and Status Changes

Status have been created to keep track og changes in surveyed features.

It is an additional (though provided for in AIA standards), single digit value, at the end of the Gisaf Category/Cad layer name.

Each Status need to have a corresponding CAD layer/Gisaf Category, with a short code associatedto it, so that field entries can be done easily.

Status have been defined as follows:

N - New Work

E - Existing o remain

D - Existing to demolish, Demolished or Changed

F- Future work, Proposed feature

T - Temporary work

M - Item to be moved

X - Not in contract

By default, Status is defined as E (Existing). Status can anyhow be changed later using gAdmin, or QGis (through the PostGis connection).

It needs to be done manually, one feature (point, line, polygon) at a time.

In the future Status changes might be incorporated in the Admin panel.

h1. Documentation - Tags retained after re-import of same geometry

Documentation - Tags retained after re-import of same geometry

The linework for infrastructure survey carried out by Eric Chacra in May 2020 was originally imported with a problem of ambiguity in the "Accuracy" table and in the "Accuracy" table.

The result was that lines did not inherit the attributes survey date, accuracy, equipment, surveyor.

Nevertheless lines were displayed on the Gisaf map, without these attributes, and tags were given to some of these lines.

The values for the two tables ("Accuracy", "Accuracy") have been corrected, ambiguity resolved.

The lines in the layers V-ELEC-UGND------E and V-COMM-CABL------E have been then reimported, the attributes have been properly assigned, and the tags have been retained.

4 August 2020

h1. Access to data

h2. 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

h2. 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.

h1. 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°

h1. 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.

h1. Linework for the Survey Area

h2. 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+

h2. Note: The line shapefiles / Geopackages shall be in CRS: TM AUSPOS

h2. 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).

h2. 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:

!https://redmine.auroville.org.in/attachments/download/9760/Line%20to%20Polygon%20Menu.png!

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

!https://redmine.auroville.org.in/attachments/download/9762/Lines%20to%20Polygon%20Window.png!

•	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)

h2. 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.

h2. Linework for the whole Survey Zone

h2. 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:

!https://redmine.auroville.org.in/attachments/download/9763/Union%20Menu.png!

The new window for “Union” will appear:

!https://redmine.auroville.org.in/attachments/download/9764/Union%20Window.png!

•	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.)

h2. 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.

h2. 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.

h2. 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.

*

h2. 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 noted, as Gisaf database does not accept the Multipolygon and Multiline geometry types.

A different way to create "Polygons" is to use the command Vector -> Geometry Tools -> Multipart to Single Parts and apply it to the layer: from "Multipolygon" it will become "Polygon" (check in layer Properties).

As on 13 March 2021, Gisaf can accept Multipolygon layers, because the command "Multipart to Single parts" has been integrated into the importing command (see Redmine ticket #11691)

h1. Creating 3D Shapefile/Geopackage

While creating a Shapefile/Geopackage, the File name/Database-table name, Geometry type and CRS have to be entered.

In order to create a 3D Shapefile/Geopackage, the additional dimensions *"Z(+M values)"/ "Include Z dimension"* has to be ticked: this way the 3D Shapefile/Geopackage is accepted by Gisaf without errors, otherwise the Shapefile/Geopackage can't be imported in Gisaf because the Z dimension is missing (the geometries in the database are all 3D).

h1. Exporting from QGis (shapefiles and/or geopackages) to CAD dxf format

An algorithm has been created by Selvarani, to see the whole process click here:

https://redmine.auroville.org.in/projects/gis/wiki/Automatic_export_from_QGis_to_dxf