extracting the outline of raster imagery using GDAL

Salams I want some help regarding developing a code in GDAL to extract the outline of any raster file or group of raster data in vector format... any ideas please ??

Graphical modeler in QGIS. I can't find a model

I'm a doing a tutorial for QGIS and at one point I have to use 'Join attributes by location' model but I do not find it in the Graphical modeler. Does it have to be there? I have to download it from somewhere?

I am using QGIS 2.8.1.

Any help would be useful. Thx.

ODK Collect GPS Accuracy

Good day. Is it possible to require a minimum accuracy of the GPS widget? I know about accuracy threshold but what I need is to prevent forward swiping/finalization of the form if GPS accuracy is low.

ArcGIS JavaScript API 3.13 error with Measurement setTool() function

When upgrading to 3.13 the following code to disable the measurement tool returns an error:

measurement.setTool("distance", false);

Here is the error:

Uncaught TypeError: Cannot read property 'domNode' of undefined

When I switch back to 3.12 it works fine. I'm thinking it's a bug in 3.13, but wanted to see if anyone else has run across this?

Spatial Join Layer Derived from Zonal Raster on Original Polygon

I'm trying to do a 1:1 spatial join between polygons created from the zonal max of a slope raster on the original zonal features. The problem is that the jagged edges cause the target features to overlap neighboring polygons as well so it just uses the first join feature in the 1:1 join.

So basically, in this picture, I want to use a spatial join to add the grid code 300 from the blue layer to the polygon (red outline) on the right and 100 to the polygon on the left. The overlap from the jagged lines are causing it to assign whichever value is first instead of whichever one has the greatest overlap.

Open/Import CityGML in AutoCAD

I have a CityGML file and want to open and further process it in AutoCAD. Any suggestions for a schmoove workflow?

For my specific use case, I only need the 2D coordinates of the file's <bldg:GroundSurface> elements' <gml:LinearRing><gml:posList>. That is, I'm only interested in the files' X and Y components. Maybe that makes it easier...

how to apply a canvas 'grid' to leaflet without curvature

I'm trying to create a grid of tiles in canvas to represent some data

the original data comes with UK OSEAST1m and OSNORTH1m, i'm the grouping the data up into aggregates of, say 40km (as per the image). I'm then taking the grouped data and and projecting it - from the grid ref to lat/lon using geodesy, and then creating a rectangle in canvas.

It works roughly, but this means that there is a grid, as such, but squares that roughly follow the curvature of the projection.

How can I make a grid, so that the squares are aligned?