Re: [Qgis-user] Bathymetry data area coverage calculator
Thanks, I'll check it out. On Sat, Jul 31, 2021, 20:42 Charles Dixon-Paver wrote: > The raster calculator is a tool for raster analysis which doesn't quite > suit your needs as I understand them. If you want to learn how to use the > raster calculator there is a tutorial available on the QGIS changelog > lessons [1]. > > That blog post I linked to before is likely the most effective or > performant option for you, and it contains links to scripts that will > perform the analysis for you. > > As an alternative, I have created a simple model which steps through the > vectorization process of reclassifying a raster and calculating the area > [2]. The data I used to test the model was the SRTM tile used in the > previously mentioned lesson [1], so you can introspect it and copy the > logic or tweak it as needed. I did a session on using the modeler for the > last Open Day [3] so you can get familiar with them if you aren't already. > > [1] https://changelog.qgis.org/en/qgis/lesson/raster-16/detail/51/?q=7.2 > [2] > https://github.com/zacharlie/effective-dollop/blob/main/qgis-models/raster_area_calculation_example.model3 > [3] https://github.com/qgis/QGIS/wiki/QOD-July-2021 > > On Sat, 31 Jul 2021 at 20:29, Peters wrote: > >> Very helpful. Yes, our data is raster. I saw a calculator tool in the >> raster toolbar but haven't been able to figure it out or if it's pertinent. >> >> On Sat, Jul 31, 2021, 19:01 Charles Dixon-Paver >> wrote: >> >>> I think you will need to provide more information on describing the >>> input data, as well as how exactly you wish to process it. >>> >>> If your coverage data is vector areas you should be able to simply use >>> the aggregate processing tool using $area as the source expression and >>> stipulate a sum aggregate function. You may also use the grouping >>> function to filter the results as needed using an expression. >>> >>> This would provide the area based on map units, so you would need to >>> reproject your data into a relevant metric projection before performing the >>> aggregation. A single hectare is simply 1 m² so simple arithmetic will >>> allow you to convert metric areas to hectares. >>> >>> If your data is another vector data type such as point clouds, you may >>> need to buffer or calculate a minimum bounding geometry or convex hull >>> before processing it as the area calculation will of course only work on >>> area features. >>> >>> For raster data, the total area would be a simple calculation of the >>> extents, or the dimensions and cell size. Again, you may need to reproject >>> the data for it to be available in meters. >>> >>> If, however, you wish to segregate raster data based on cell value, you >>> may want to recode and vectorize the data, or alternatively perform some >>> form of custom analysis as described in the following article: >>> https://www.kartoza.com/en/blog/calculating-area-of-rasters-in-qgis/ >>> >>> Regards >>> >>> On Sat, 31 Jul 2021 at 19:15, Peters wrote: >>> Does anyone know of such a calculator as a plugin or option? At the moment I am using QGIS app. Our client has asked for area coverage in sq. mtrs or hectares. Appreciate any info you may have. -- *regards,* *K. Peters* *cell: (Morocco) +212.671.218606* ___ Qgis-user mailing list Qgis-user@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user. >>> ___ Qgis-user mailing list Qgis-user@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
Re: [Qgis-user] ArcGIS RESTserver: table only layer possible or not?
Hi Richard, looking at the code [1] it seems that only the resources listed in the "layers" list of the FeatureServer are added as items and shown as available layers in QGIS, while the resources listed in the "tables" list are not added as items and not shown as available layers in QGIS. So, I think the ArcGIS REST provider could be (easily) improved to also list and manage the "tables" of a FeatureServer. Regards. Andrea Giudiceandrea [1] https://github.com/qgis/QGIS/blob/d80ebabd7d0f8b7835413902d355f056a4cfb42a/src/core/providers/arcgis/qgsarcgisrestquery.cpp#L349 ___ Qgis-user mailing list Qgis-user@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
Re: [Qgis-user] Bathymetry data area coverage calculator
The raster calculator is a tool for raster analysis which doesn't quite suit your needs as I understand them. If you want to learn how to use the raster calculator there is a tutorial available on the QGIS changelog lessons [1]. That blog post I linked to before is likely the most effective or performant option for you, and it contains links to scripts that will perform the analysis for you. As an alternative, I have created a simple model which steps through the vectorization process of reclassifying a raster and calculating the area [2]. The data I used to test the model was the SRTM tile used in the previously mentioned lesson [1], so you can introspect it and copy the logic or tweak it as needed. I did a session on using the modeler for the last Open Day [3] so you can get familiar with them if you aren't already. [1] https://changelog.qgis.org/en/qgis/lesson/raster-16/detail/51/?q=7.2 [2] https://github.com/zacharlie/effective-dollop/blob/main/qgis-models/raster_area_calculation_example.model3 [3] https://github.com/qgis/QGIS/wiki/QOD-July-2021 On Sat, 31 Jul 2021 at 20:29, Peters wrote: > Very helpful. Yes, our data is raster. I saw a calculator tool in the > raster toolbar but haven't been able to figure it out or if it's pertinent. > > On Sat, Jul 31, 2021, 19:01 Charles Dixon-Paver > wrote: > >> I think you will need to provide more information on describing the input >> data, as well as how exactly you wish to process it. >> >> If your coverage data is vector areas you should be able to simply use >> the aggregate processing tool using $area as the source expression and >> stipulate a sum aggregate function. You may also use the grouping >> function to filter the results as needed using an expression. >> >> This would provide the area based on map units, so you would need to >> reproject your data into a relevant metric projection before performing the >> aggregation. A single hectare is simply 1 m² so simple arithmetic will >> allow you to convert metric areas to hectares. >> >> If your data is another vector data type such as point clouds, you may >> need to buffer or calculate a minimum bounding geometry or convex hull >> before processing it as the area calculation will of course only work on >> area features. >> >> For raster data, the total area would be a simple calculation of the >> extents, or the dimensions and cell size. Again, you may need to reproject >> the data for it to be available in meters. >> >> If, however, you wish to segregate raster data based on cell value, you >> may want to recode and vectorize the data, or alternatively perform some >> form of custom analysis as described in the following article: >> https://www.kartoza.com/en/blog/calculating-area-of-rasters-in-qgis/ >> >> Regards >> >> On Sat, 31 Jul 2021 at 19:15, Peters wrote: >> >>> Does anyone know of such a calculator as a plugin or option? At the >>> moment I am using QGIS app. Our client has asked for area coverage in sq. >>> mtrs or hectares. Appreciate any info you may have. >>> >>> -- >>> *regards,* >>> *K. Peters* >>> >>> *cell: (Morocco) +212.671.218606* >>> ___ >>> Qgis-user mailing list >>> Qgis-user@lists.osgeo.org >>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user >>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user. >>> >> ___ Qgis-user mailing list Qgis-user@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
Re: [Qgis-user] Bathymetry data area coverage calculator
Very helpful. Yes, our data is raster. I saw a calculator tool in the raster toolbar but haven't been able to figure it out or if it's pertinent. On Sat, Jul 31, 2021, 19:01 Charles Dixon-Paver wrote: > I think you will need to provide more information on describing the input > data, as well as how exactly you wish to process it. > > If your coverage data is vector areas you should be able to simply use the > aggregate processing tool using $area as the source expression and > stipulate a sum aggregate function. You may also use the grouping > function to filter the results as needed using an expression. > > This would provide the area based on map units, so you would need to > reproject your data into a relevant metric projection before performing the > aggregation. A single hectare is simply 1 m² so simple arithmetic will > allow you to convert metric areas to hectares. > > If your data is another vector data type such as point clouds, you may > need to buffer or calculate a minimum bounding geometry or convex hull > before processing it as the area calculation will of course only work on > area features. > > For raster data, the total area would be a simple calculation of the > extents, or the dimensions and cell size. Again, you may need to reproject > the data for it to be available in meters. > > If, however, you wish to segregate raster data based on cell value, you > may want to recode and vectorize the data, or alternatively perform some > form of custom analysis as described in the following article: > https://www.kartoza.com/en/blog/calculating-area-of-rasters-in-qgis/ > > Regards > > On Sat, 31 Jul 2021 at 19:15, Peters wrote: > >> Does anyone know of such a calculator as a plugin or option? At the >> moment I am using QGIS app. Our client has asked for area coverage in sq. >> mtrs or hectares. Appreciate any info you may have. >> >> -- >> *regards,* >> *K. Peters* >> >> *cell: (Morocco) +212.671.218606* >> ___ >> Qgis-user mailing list >> Qgis-user@lists.osgeo.org >> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user >> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user. >> > ___ Qgis-user mailing list Qgis-user@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
Re: [Qgis-user] Bathymetry data area coverage calculator
I think you will need to provide more information on describing the input data, as well as how exactly you wish to process it. If your coverage data is vector areas you should be able to simply use the aggregate processing tool using $area as the source expression and stipulate a sum aggregate function. You may also use the grouping function to filter the results as needed using an expression. This would provide the area based on map units, so you would need to reproject your data into a relevant metric projection before performing the aggregation. A single hectare is simply 1 m² so simple arithmetic will allow you to convert metric areas to hectares. If your data is another vector data type such as point clouds, you may need to buffer or calculate a minimum bounding geometry or convex hull before processing it as the area calculation will of course only work on area features. For raster data, the total area would be a simple calculation of the extents, or the dimensions and cell size. Again, you may need to reproject the data for it to be available in meters. If, however, you wish to segregate raster data based on cell value, you may want to recode and vectorize the data, or alternatively perform some form of custom analysis as described in the following article: https://www.kartoza.com/en/blog/calculating-area-of-rasters-in-qgis/ Regards On Sat, 31 Jul 2021 at 19:15, Peters wrote: > Does anyone know of such a calculator as a plugin or option? At the > moment I am using QGIS app. Our client has asked for area coverage in sq. > mtrs or hectares. Appreciate any info you may have. > > -- > *regards,* > *K. Peters* > > *cell: (Morocco) +212.671.218606* > ___ > Qgis-user mailing list > Qgis-user@lists.osgeo.org > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user > ___ Qgis-user mailing list Qgis-user@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
[Qgis-user] Bathymetry data area coverage calculator
Does anyone know of such a calculator as a plugin or option? At the moment I am using QGIS app. Our client has asked for area coverage in sq. mtrs or hectares. Appreciate any info you may have. -- *regards,* *K. Peters* *cell: (Morocco) +212.671.218606* ___ Qgis-user mailing list Qgis-user@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
Re: [Qgis-user] Clipping WMS Layer for Export to Geo PDF
The latest releases of QGIS support "clipping settings" for map frames in layouts [1]. This means that you can "clip" the map frame to a specific shape within the layout, or an atlas item. You cannot clip the map to a specific feature, however, but I expect you could get around this by creating an atlas from a layer with only one feature. I'm not very familiar with Avenza so I'm unsure how well this would suit your needs. One other thing to note is that your "area of interest" polygon does not necessarily need to be differenced with a bounding area separately, as you may simply use the "Inverted Polygons" style to mask off your relevant area of interest. Regards [1] https://qgis.org/en/site/forusers/visualchangelog316/index.html#clip-layout-maps-to-shape On Sat, 31 Jul 2021 at 12:02, kirk wrote: > Hi Stewart > I assume you are using a rater as a background layer and therefore you > will always end up with a rectangle as your final extent. If you clip to > an irregular polygon, you will still have a rectangle but the outer area > that had been clipped out will be transparent. This is how raters work as > they are regular grids. The disadvantage of clipping to an irregular > polygon is that you will create an additional alpha channel which defines > the transparency but adds to the file size. > > I would consider making a number of smaller maps with some overlap to use > with avenza. > > Kirk Schmidt > > > > Sent from my Galaxy > > > Original message > From: Stewart Holt > Date: 2021-07-30 4:38 p.m. (GMT-04:00) > To: User List QGIS > Subject: [Qgis-user] Clipping WMS Layer for Export to Geo PDF > > I am working on a GeoPDF map to use in the Avenza map app. It is an 80 > mile hiking trail which stair steps from SW to NE. I am using a WMTS layer > as a background. I want to avoid having the PDF as large as a rectangle > containing this trail. I created a polygon and used it to select the extent > for the map, but it did not clip the map but instead it created a > rectangular extent containing the polygon. > > Next I created a larger rectangular polygon covering the area and cut out > a ring for the trail and included this layer in the map. The result was the > inclusion of all of the WMTS map layer as before with my mask layer able > to block unwanted areas. This does not reduce file size, ofcourse. > > I think what that did is the correct behavior. What I need is a way to > clip the WMTS layer on the fly. I think having the export to PDF being able > to do this would be the best approach. > > Can anyone think of how to accomplish this without exporting the WMTS > layer and then clipping it with a polygon? > > Thanks, > > Stewart > ___ > Qgis-user mailing list > Qgis-user@lists.osgeo.org > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user > ___ Qgis-user mailing list Qgis-user@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
[Qgis-user] ArcGIS RESTserver: table only layer possible or not?
Hi, In a chat somebody asked IF it would be possible to load table-only layers, I tried to use the normal dialog (to find the uri), but QGIS just does not show the layers if table only. Is this a 'feature request to be'? Or am I missing something? To test, connect to: https://services2.arcgis.com/XZg2efAbaieYAXmu/ArcGIS/rest/services/ retrieve the layer tree from it, see there is a db icon for TeleTracking_Spreadsheet_HistoricalFields, but note that is no layer appearing for it, while the user tells me that there should be a table-only 'layer' there? Any tips? Regards, Richard Duivenvoorde ___ Qgis-user mailing list Qgis-user@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
Re: [Qgis-user] Clipping WMS Layer for Export to Geo PDF
Hi StewartI assume you are using a rater as a background layer and therefore you will always end up with a rectangle as your final extent. If you clip to an irregular polygon, you will still have a rectangle but the outer area that had been clipped out will be transparent. This is how raters work as they are regular grids. The disadvantage of clipping to an irregular polygon is that you will create an additional alpha channel which defines the transparency but adds to the file size.I would consider making a number of smaller maps with some overlap to use with avenza.Kirk SchmidtSent from my Galaxy Original message From: Stewart Holt Date: 2021-07-30 4:38 p.m. (GMT-04:00) To: User List QGIS Subject: [Qgis-user] Clipping WMS Layer for Export to Geo PDF I am working on a GeoPDF map to use in the Avenza map app. It is an 80 mile hiking trail which stair steps from SW to NE. I am using a WMTS layer as a background. I want to avoid having the PDF as large as a rectangle containing this trail. I created a polygon and used it to select the extent for the map, but it did not clip the map but instead it created a rectangular extent containing the polygon.Next I created a larger rectangular polygon covering the area and cut out a ring for the trail and included this layer in the map. The result was the inclusion of all of the WMTS map layer as before with my mask layer able to block unwanted areas. This does not reduce file size, ofcourse.I think what that did is the correct behavior. What I need is a way to clip the WMTS layer on the fly. I think having the export to PDF being able to do this would be the best approach.Can anyone think of how to accomplish this without exporting the WMTS layer and then clipping it with a polygon?Thanks,Stewart ___ Qgis-user mailing list Qgis-user@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
