9
votes
Finding additions and updates between two vector layers using QGIS
In QGIS, you have a number of options:
From the Processing Toolbox use Orfeo's MultivariateAlterationDetector (just type 'change' into the search box to find it) - see the documentation here.
From ...
- 34k
7
votes
Determining what lines have changed in updated shapefile using QGIS
There is a new tool which was added in QGIS 3.12 called "Detect dataset changes" that does exactly what you want. It accepts any geometry type including line. The tool
Compares two vector ...
- 41.4k
6
votes
Change Detection using Raster Calculator
Try reclassifying the rasters to a different scale of numbers, such as
urban = 1
ag = 10
forest = 100
water = 1000
Then just subtract the rasters in Raster Calculator:
0 will mean unchanged.
9 ...
- 1,383
4
votes
Accepted
Find most recent update in WMS or WFS
A few approaches which may help:
Service level
updateSequence attribute: OGC Web Service (OWS) Specifications provide an updateSequence attribute as part of GetCapabilities responses which ...
- 1,297
4
votes
Finding additions and updates between two vector layers using QGIS
For QGIS there is the tool Detect Dataset Changes available (introduced with QGIS 3.12):
https://www.qgis.org/en/site/forusers/visualchangelog312/index.html#feature-add-new-algorithm-detect-dataset-...
- 2,005
3
votes
Bare Soil Detection
I would recommend investigating Synthetic Aperture Radar (SAR) data and soil indices such as Normalized Radar Backscatter soil Moisture Index (NBMI). Radar has the benefit of being able to penetrate ...
- 51.8k
3
votes
Analysing differences between 2 dataset versions
You don't say what GIS software your department uses, so I'll respond with answers for both QGIS and ArcMap.
QGIS at 3.16.1 has a tool, Detect Dataset Changes, which I have use with great success. ...
- 8,356
3
votes
Accepted
How to calculate forest loss in google earth engine
You can find global forest loss/gain from 2000-2015 in the following raster:
var hansen = ee.Image("UMD/hansen/global_forest_change_2015_v1_3");
How you can use it is explained in this Google Earth ...
- 527
3
votes
Accepted
Population Change
The OECD defines it as follows:
The difference between the size of the population at the end and the beginning of a period. It is equal to the algebraic sum of natural increase and net migration (...
- 166
2
votes
Population Change
Usually demographers use net-migration which is the difference between in and out migration.
Note in many countries (such as the UK) this is a (poor) guess as they don't have an easy way of checking ...
- 83.2k
2
votes
Accepted
DetectFeatureChanges_management gives out error 000366 "Invalid geometry type"
I think it would better serve you to use the intersect tool under Analysis. This will produce the polygon slivers of the border changes. You'll have to use two SearchCursors to cycle through the ...
- 1,335
2
votes
Determining what lines have changed in updated shapefile using QGIS
Just to sum up all methods that were suggested in comments:
@Germán Carrillo
Vector > Geoprocessing Tools > Symmetrical difference
The same result can be achieved with SAGA GIS Symmetrical ...
- 34k
2
votes
Accepted
Calculate difference of subsequent images in a collection
You can calculate the backward difference in a ImageCollection by converting it to a list and mapping over that:
var ic_list = ic.sort('system:time_start').toList(ic.size())
print(ic_list)
// ...
- 9,947
2
votes
Comparing current image in collection to previous image in collection using Google Earth Engine
Your approach is not a common one. You are using a lot of client side code that is not recommended (see here). Besides, you did not provided enough information, so I made some assumptions and made up ...
- 10.2k
2
votes
How to identify landuse change with Sentinel data - specifically grassland/woodland to arable cropland changes
Full disclosure: I work for a company which offers these kinds of services.
Your question is complicated and there are multiple topics and considerations, so lets break it down:
1. Technical ...
- 256
2
votes
Accepted
QGIS/SAGA Cross-tabulation error
i'll wager it's the space in the file path (between Tom and new). The following error seems to hint at it
syntax error near unexpected token `new'
In some versions of processing, the file path isn't ...
- 20.6k
2
votes
Accepted
How to perform change detection using classified land cover map in Google Earth Engine?
You could do something like this:
var fromClassification = dummyClassification(2016)
var toClassification = dummyClassification(2019)
var classes = [1, 2, 3] // Class values in your classification. ...
- 14.8k
2
votes
Shoreline change analysis in ArcGIS Pro
This would call for a classification analysis. You could perform a classification analysis to determine waterlines (water vs. ground) for each year. There is a Classify Pixels Using Deep Learning tool ...
- 448
2
votes
Accepted
Change Detection Chart from lists in Google Earth Engine
I would use an ui.Chart.feature.groups chart. That requires you to rearrange your data a bit. Here's one way to do that:
var labelByCode = ee.Dictionary({
1: 'Air',
2: 'Vegetation',
3: 'Urban',
}...
- 14.8k
2
votes
Accepted
Understanding 'ccdc' algorithm in Google Earth Engine
It's somewhere in between, since it's derived from the V12.30 MATLAB implementation, and you can manually specify the number of observations required to detect a change (it defaults to 6). There is ...
- 12.3k
2
votes
Accepted
Land cover change detection using raster calculator in QGIS
I think what J. Kelly responded on this thread also applies here. The idea behind it is to reclassify to numbers which generate unique values when subtracted. This way, instead of "Forest --> ...
- 188
2
votes
Detecting Land Use Land Cover Changes from Copernicus Corine Maps in GEE - Calculating Areas of LULC Change Pairs
You're passing an array to group() while it expects an integer. I think something like this could do what you're after:
var areas = ee.FeatureCollection(ee.List(
ee.Image.pixelArea()
.addBands(...
- 14.8k
1
vote
Finding difference between two rasters using ArcGIS Spatial Analyst?
If you are asking how to identify which class becomes what then have a look at the Tabulate Area (Spatial Analyst) tool in the Help file. It generates an output table showing you the number of pixels ...
- 44.6k
1
vote
Estimating building and vegetation volume with unclassified LiDAR datasets?
Building
As suggested by Michael Stimson use the Classify LAS Building tool (3D Analyst required):
Classifies building rooftop points in aerial lidar data.
To have an idea about how precise and ...
- 10.3k
1
vote
Calculating LULC change 1973-2014 of a classified map (raster converted to shapefile) in ArcGIS 10.6
I see a bunch of polygon boundaries in there. Since this information started out as a classified raster you probably will have better luck doing the tabulations in raster.
First mask your classified ...
- 1,560
1
vote
Visualizing specific class from unsupervised classification in Earth Engine
Easily done. Add this to the bottom of your script. This checks every pixel, and if it equals 9, then it passes the test the new pixel is set to 1. otherwise, 0.
var subset = result.select("...
- 2,242
1
vote
Accepted
Comparing between two polygon class values
Assuming each polygon has data for both fields, and both are integers 0-4, perhaps you could construct a plot that has 3 different sorts of symbology:
1. where field 1 = field 2 (no change)
2. field2 >...
- 1,485
1
vote
Perform change detection using LandTrendr in Google Earth Engine?
var aoi =
/* color: #d63000 */
/* shown: false */
/* displayProperties: [
{
"type": "rectangle"
}
] */
ee.Geometry.Polygon(
[[[-47.05253256069382, -10....
1
vote
Classifying type of crop on satellite images using Python
I have been using Dzetaska classification tool.
Seems to work pretty good. > 80%
https://plugins.qgis.org/plugins/dzetsaka/
I have been using it on QGIS. I do not know anything about python.
Step ...
- 167
1
vote
Change detection between two binary images
This is what combined raster table looks like:
So Value of 1 corresponds to dry land before and after; 2 - was dry become flooded etc.
Alternatively one can use fact that sum of any two numbers in ...
- 23.3k
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