17
votes
Using CASE statements to sort multiple values in QGIS Field Calculator
Use like this:
CASE
WHEN "stat_land_" IN ('A1', 'A2', 'A9', 'E', 'E2')
THEN 'Residential'
WHEN "stat_land_" IN ('C', 'C1')
THEN 'Vacant Land'
...
- 78k
7
votes
Accepted
Extract one class from global LULC in google earth engine
There is a lot of ways to do this. If you want to preserve class ID, you need to mask the desired class. For example:
var crop_mask = cover.eq(13); // create a mask for crops
var crop = cover.mask(...
- 13.8k
6
votes
Accepted
Is Landsat 30m resolution satellite images accurate enough to map land cover on a 40 km² watershed?
The size of the area is not the primary issue for the selection of a satellite sensor resolution. You should rather think about the size of the objects that you are mapping and their contrast with the ...
- 49.9k
6
votes
Accepted
Calculating block statistics from land cover raster using R?
You can use the aggregate function in the raster package to do this. For example, to produce a raster at half the resolution of the original, showing the proportion of cells covered with land class 1: ...
- 13.2k
5
votes
Accepted
Appropriate CRS for land-use change within EU?
ETRS 89 refers to a Geographic Coordinate System, while UTM 32 is a Projected Coordinate System.
I would discard both because UTM only cover approximately 6 degrees of longitude before you start to ...
- 49.9k
4
votes
Accepted
Replacing values of raster in R to produce landuse-like raster map?
You must invert your order:
Z <- runif(100, 0, 2)
Z[Z>0.12]<-3
Z[Z==0.12]<-2
Z[Z<0.12]<-1
Your problem was due to in the first sentence (Z[Z<0.12]<-1) you made values ...
- 376
4
votes
Sentinel-2 images
It is always preferable to use bottom of atmosphere reflectance (BOA) products (e.g. L2A) instead of top of atmosphere (TOA) reflectance products (e.g. L1C). For example, the image below shows a L1C ...
- 51.8k
4
votes
"Image.select: Pattern 'blue' did not match any bands" error during LULC change detection using Earth Engine
The problem is that there are no images available from 1900 - 1990; thus, the classifier outputs an error when it tries to classify an empty image. An easy fix would be to simply change the startyear ...
- 2,341
4
votes
Looking for QGIS equivalent of ArcGIS "Group values" tool
We can use Reclassify by table.
In this example values 1,2,4 are set to 1; value 3 is set to 2, and all other values are set to null.
- 3,197
3
votes
Calculating block statistics from land cover raster using R?
I agree that raster::aggregate() works well in most cases, especially when a user-defined function is involved as in the answer given by @dbaston. However, you might want to have a look at the velox ...
- 5,213
3
votes
Accepted
Getting Land Use data from National Land Cover dataset
It looks like the @data@attributes element is metadata about the data set as a whole, not the particular extract. I tried get_nlcd with a smaller polygon region and the table in @data@attributes was ...
- 66.5k
3
votes
Creating a series of buffers along a stream polygon at set intervals in ArcGIS Pro
Forget about rectangles, they are only possible if river is straight line.
Just split your lines at equal interval (Generate Points Along line and Split by points) and run Euclidean allocation:
...
- 23.3k
3
votes
Accepted
Looking for QGIS equivalent of ArcGIS "Group values" tool
Open the layer symbology
Select the classes you wish to group
Right click to change label for all of the classes at once
Do the same for the colour
The classes will appear merged in the legend
- 69.6k
3
votes
Accepted
Calculating percentage of landuse type within buffer using Python
You can use geopandas with union and groupby:
import geopandas as gpd
landuse = gpd.read_file(r"/home/bera/Desktop/gistest/my_riks_smallsample.shp")
landuse_class_field = "kkod"
...
- 77.8k
2
votes
Accepted
Where on-line can I find a GIS land use .lyr that shows standard colors for each land use code?
I did not see any standards for land use classification in general because it depends on each country's standard. You need to refer to the standards applied in Ministry of land or Land Bureau in the ...
- 41.4k
2
votes
Accepted
Molusce crashes QGIS when starting the changes raster calculation
The solution is the reclassification of values!
After searching the answer also on YouTube I got responded by a user which wrote me:
An additional tip: a friend had labeled categories in their ...
- 533
2
votes
How do I classify a highly heterogeneous built-up area?
There are two facets for this issues: one is conceptual and the other is technical.
The conceptual issue is that you need to define what you mean by built up area in your legend. A good starting ...
- 49.9k
2
votes
Accepted
How do I classify a highly heterogeneous built-up area?
That would likely be your best bet, outside of object-based classification.
However, another option would be to use a more advanced algorithm for classification, such as the Support Vector Machine, ...
- 551
2
votes
QGIS, Buffer, and Land Use around coordinate points
This is a common procedure for landscape ecology.
The LecoS plugin allows you to calculate the amount (among other metrics) of each land use class (the different values of your land use raster) ...
- 123
2
votes
Accepted
Calculate land use percentage within an area?
You can divide the area of the land use features by the area of the basin, then multiply by 100 to derive percent. If the area of your land use features or the basin are not already in the attribute ...
- 1,529
2
votes
Random Forest Classification of Landsat8 Image gives invalid/noise output
You stated:
I used randomly generated points and collected pixels from Maximum
Likelihood Classification from ArcGIS 10.3 which was used as training
dataset.
I suspect creating training data ...
- 51.8k
2
votes
Crop data for Europe / Germany
You should almost certainly start your research by looking at the INSPIRE geoportal ~ http://inspire-geoportal.ec.europa.eu/discovery/
Any public body in German that has any data that falls under the ...
- 13.6k
2
votes
interpreting Normalized Differentiated Bareness Index and Normalized Differentiated Impervious Surfaces Index?
The word normalized means fitting all your observations between -1 and 1, hence all normalized indexes will have this range.
As for literature:
Use of Normalized Difference Bareness Index in Quickly ...
- 3,211
2
votes
Merge adjacent polygons into a land use map
Assuming you already have an attribute field containing the area of your polygons in your data, this could be the workflow:
Choose the "Select features by value" function in the toolbar, in the popup ...
- 2,351
2
votes
Accepted
How to get R to recognize a discrete raster layer
You can use levelplot from the rasterVis package to plot with categorical labels:
> r = raster(matrix(sample(1:3,25,TRUE),5,5))
> levels(r)=data.frame(ID=1:3, code=LETTERS[1:3])
> rasterVis::...
- 66.5k
2
votes
Accepted
2 raster files, find suitable area
you can reclassify both rasters and sum them.
Example:
Reclassify Urban to 1 and others to 0.
Same for the 2nd layer. High flood 1, others 0.
So if you sum rasters the area under 2 value will be ...
- 391
2
votes
Calculate land cover for grid cells in QGIS
You can use Raster layer zonal statistics in which you can select the land cover raster layer as input file, and use the shapefile as zone layer. It will calculate the area (in the raster unit) of ...
- 41.4k
2
votes
Why using buffers in land use / land cover classification task?
Specifically about the tutorial provided as example:
The positive buffer along Slovenia borders is being applied possibly to avoid empty pixels in the edge of corresponding patches (i.e, pixels only ...
- 10.3k
2
votes
Using R to sum raster pixels of specific values
It is just a matter of writing a function that returns the proportions and using lapply to apply it to the list returned from exact_extract.
Add libraries and create example data
library(sf)
library(...
- 32k
2
votes
Accepted
Importing landuse (raster) to polygon using ArcGIS Pro
You can polygonize the raster, clip it by boundary, and then get the land area of each land use per boundary. Tabulate Area in ArcGIS is the closest tool I can think of.
- 1,217
Only top scored, non community-wiki answers of a minimum length are eligible