Questions tagged [accuracy]
The degree of closeness of measurements of a quantity to that quantity's actual value
175
questions
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14 views
When creating a confusion matrix, can you have more ground-truth points than the recommended 10-times the number of classes you have?
Using ArcGIS Pro, I classified a field of grain sorghum (supervises, pixel-based support vector machine) using 5 classes: Soil, Shadows, Leaves, Heads, and Ground targets (this was a UAS study). The ...
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0answers
17 views
eCognition Accuracy Assesment Tool problem
I'm narrowing down a vegetation RF classification in eCognition along a river course, it's going very well but I've run into a problem with my Accuracy Assessment. The gist of it is that my class sums ...
1
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1answer
34 views
Implementing proportional stratified random sample in R
I've completed a landcover classification on an Landsat Image and would like to start an accuracy assessment. I'd like a stratified random sample that has a sample number that varies based on each ...
1
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1answer
40 views
How to randomly stratify sampling within landcover classes?
I'm working on an accuracy assessment of a classified landsat image and I'd like input on the best possible way to generate random points across both the classified image and a ground truth image I ...
2
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0answers
40 views
Combine polygons from different sources
I am currently working on a project where I try to reconstruct historical borders of the austro-hungarian empire between 1815 and 1918. Therfore I use the comination of digitized old maps an legal ...
1
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1answer
38 views
Checking accuracy of supervised classification method in ArcGIS Pro
I have a question about my image classification method in ArcGIS Pro 2.4.
I'm looking at a field of grain sorghum and doing a project that requires me to define certain features within the image for ...
1
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0answers
41 views
QGIS wrong measurments on Google satellite images
I am new to QGIS but I understand the basic principles. I'm working with QGIS 3.8.3 on OpenSUSE Tumbleweed Linux using the KDE environment.
Still trying to figure out QGIS, I'm opening a brand new ...
1
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0answers
33 views
Accuracy of ArcGIS Collector
About ArcGIS Collector app, what's the difference between accuracy in the setting tab and horizontal/vertical accuracy as indicated left-bottom on the map while surveying?
For example, if I set the ...
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0answers
39 views
Does HDOP correlate with GPS position accuracy?
I collected 1000+ position data from GPS receivers and realized that a position with lower HDOP does not necessarily have higher accuracy.
So my question is does HDOP correlate with GPS position ...
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0answers
35 views
Simultaneous raster downsampling/downscaling and upsampling/upscaling for false accuracy minimisation
I want to have a raster stack of two different resolutions.
One is from VSNIR and one from SWIR sensors (hyperspectral).
The VSNIR has a resolution of 25 cm and the SWIR of 80 cm and both data have ...
1
vote
1answer
50 views
Sampling stratified random points using R for accuracy assessment
I want to sample stratified random points using R. I found the sampleStratified function from the R raster package.
This functions samples the same amount of points for each class of my ...
2
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1answer
44 views
Options for precise relative position calculations
I'm investigating an industrial application that has a requirement to calculate with precision the relative distance on the ground between two outdoor points in the following scenario:
The first ...
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0answers
330 views
Accuracy of Google Maps geo-coordinates vs high precision GPS receiver
I need to know how accurate coordinates obtained from Google Maps/Earth are. Are they 'quasi absolutely' (I know there is no absolut location determination)?
In other words, if I record the ...
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0answers
51 views
Classification result from SAGA GIS shifted by 5 meters if used in ArcMap?
I use a band composite of 10 Sentinel-2 bands for my classifications. If I use the same composite in SAGA to make a classification this classification result is shifted by 5 meters to the left and to ...
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1answer
44 views
GPS accuracy deviation the same in an area?
I am using a GPS receiver to perform a speedtest over a few meters. I’ve read that the GPS is accurate up to 4 meters. Is the deviation the same in an open area and also over a short period of time? ...
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0answers
114 views
How can I compute confusion matrix using Python [closed]
My project is about "Extracting water and urban features from satellite images". I have extracted urban and water features using Python code.
Now, I want to do accuracy assessment. I know two primary ...
2
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0answers
25 views
Is there a faster way to assess accuracy of image classification in ArcGIS?
I am trying to perform accuracy assessment on a raster RGB image after supervised classification. I know the normal workflow in ArcGIS would be to create accuracy assessment points, then evaluate each ...
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0answers
16 views
Compare two forest loss classifications and fill missing years: accuracy assesment or correlation?
I have a time series of forest loss rasters originating from two different classifications with some missing yearly data. Rasters represents forest loss (1) or no disturbance (0) in specific year. I ...
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0answers
64 views
Computing GPS points accuracy
I have stand alone GPS points and RTK points collected at the same time and I want to compute the accuracy (1 sigma) of the GPS points. Using the haversine formula, I computed the distance between the ...
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1answer
80 views
Mapbox Vector Tiles appear to lack accurate intersection nodes?
Mapbox Vector Tiles appear to lack accurate intersection nodes.
Is this a bug?
i.e. should the tile's geojson include a shared node between two intersecting streets?
Details:
Using MVT's from http:...
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0answers
26 views
What is the accuracy and precision of bearings measured using Google Earth
For North America, what are the accuracy and precision that the bearings of decameter- to kilometer-long features, e.g lineaments and oriented lakes, be measured using Google Earth?
Can these ...
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0answers
26 views
Statistic validation for spectral trajectories/trend from ground truth dataset
I'm doing an extraction of spectral trajectories for disturbed forest pixels using multitemporal (single scene for 20 years) Landsat Surface Reflectance products.
Usually, forest disturbances are ...
2
votes
1answer
141 views
How to create circles around points
I'm new to QGIS so please bear with me.
I'm using QGIS 3.6.
So I imported a CSV-file with latitude longitude coordinates (WGS 84), created markers and set them to have different colors (to show ...
1
vote
1answer
114 views
Customized Albers Equal Area Conic projections are cosmetic only or do they affect area calculations too?
I will be doing area calculations for 100+ countries using country polygons taken from GADM, a database of global administrative areas. I am using ArcGIS. The GADM data is in WGS84 and is unprojected. ...
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0answers
21 views
Assessing mapping accuracy of a DEM with different resolutions
I am mapping conical shaped depressions on the seafloor and would like to know at what resolution of the DEM is my mapping accuracy affected by. For example if I have a DEM of 7 metres, what does the ...
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0answers
42 views
Is the accuracy or PDOP included in smartphone or GPS camera?
I would like to properly geolocate picture Exifs on a smartphone or GPS camera and would like to record the accuracy of the GPS position as well.
I have downloaded a few photos from camera review ...
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0answers
81 views
QField Coordinate Reference System
Does anyone know how location services on your mobile device compare to a chosen coordinate system set in the QGIS project? I am wondering how to improve the accuracy of my device compared to the ...
3
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1answer
2k views
How precise is GPS?
Most search results I get on this talk about the accuracy, that is how close the locations outputted by the GPS are to the real positions, of GPS. However, I'm working on a project that only requires ...
3
votes
2answers
116 views
Heuristic relationship between number of satellites and GPS precision?
I'm a statistician conducting an analysis on animal movement based on data collected using ATS Wildlink 500 collars. As part of this analysis, I'm estimating GPS error assuming that the error in the ...
2
votes
1answer
853 views
Why ground model from point cloud in Global Mapper is inaccurate?
I have a LAS file that I assumed was based on LiDAR, but it is actually based on ADS (airborne digital sensor) imagery, according to the body that captured the data.
I load the file in to Global ...
3
votes
1answer
93 views
GNSS accuracy, what is it?
Using a Trimble GeoExplorer 6000 Series GeoXT Handheld, I recorded uncorrected GNSS positions, for example:
Horizontal estimated accuracy in the field 4 meters.
Vertical estimated accuracy in the ...
1
vote
1answer
159 views
Combing multiple LAS files with different vertical and horizontal accuracy?
The data set in question was made using .las and .zlas files from respectable sources.
Data set 1 was collected in the Fall of 2014. The RAW flight line swath data was processed to create classified ...
4
votes
2answers
960 views
Surveys showing GPS accuracy in different models of smartphones?
Are there any surveys that give accuracy in meters for different smartphones (e.g, iPhone 6: 8 meters, Samsung Galaxy S8: 7 meters) regardless of what the statistical method is being used?
1
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2answers
42 views
Efficient way to check sample points on many Landsat scenes?
I want to do an accuracy assessment for an annual burned area map (large area - whole country). I have random sampling points which I need to check in simple burned - not burned categories but ...
1
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1answer
308 views
How to improve the accuracy of geolocation on openlayers 5
I wonder if it is possible to improve the accuracy of geolocation on openlayers 5, currently it is off by 5000 meters although I enabled highaccuracy option.
var geolocation = new ol.Geolocation({
...
3
votes
1answer
211 views
What exactly is an RTK GNSS receiver?
I have seen many GNSS/INS sensors come with "RTK GNSS receivers" which enable you to achieve RTK. I have been looking at the sensor I have got which claims to be RTK capable, the user manual says it ...
0
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0answers
38 views
Points to line accuracy concerns in ArcMap
I have a csv of a GPS trace with lat-longs that I want to convert into a line so I can measure the distance. My workflow was as follows:
1) Import csv into ArcMap 10.4
2) Convert latlongs to points ...
1
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0answers
34 views
NoData values in classification accuracy assessment
I want to assess the accuracy of a settlement classification I made (classification map) by comparing it to another product's settlement classification (reference map). Both maps have two "normal" ...
1
vote
1answer
289 views
GEE: apply ee.Reducer.mean to a list
After classification of an image in GEE, I got 2 lists of user's and producer's accuracies (1*7 and 7*1 dimensions). How can I calculate an average value for each of them now?
print('Validation ...
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0answers
239 views
Relative/Local Accuracy (of a map): Definition & Error Calculation
Here there is a good definition for Relative/Local accuracy of map:
This is the accuracy of a point on the map relative to other points
within the map/model.
It sound like theoretically we can ...
1
vote
1answer
463 views
What is the maximum theoretical refresh rate for GPS [closed]
I understand that most devices have 1 Hz refresh rate for GPS positioning. I tried to read about the actual GPS implementation but I could not figure out how often the location can be determined.
...
2
votes
2answers
159 views
Why such a large difference between overlapping LiDAR DEM values?
Background:
Using Arc Desktop 10.5.1, I have been tasked with mosaicking two adjacent LiDAR rasters (I'll call them A and B). They were flown, processed and supplied under contract by different ...
2
votes
0answers
74 views
Where exactly is the GPS position located on a GPS device?
I have a very precise GPS which in theory when using RTK achieves 2cm accuracy when reporting its GPS position. But where exactly on the GPS device is this position? In other words, when the GPS ...
2
votes
0answers
577 views
Assessing accuracy of image classification using ArcGIS Desktop? [closed]
I have classified images in ArcGIS Desktop with the support vector machine classifier, and am now struggling with the accuracy assessment. I have only been able to find tutorials on how to do it ...
0
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1answer
357 views
Which type of point cloud is more accurate: from airborne LiDAR or aerial photos?
I have been offered two types of point cloud for my 3D Project. The data will be used by the environmental agency in various projects e.g. flood-risk analysis, dyke conservation, and nature ...
1
vote
1answer
39 views
Data gets skewed when re-adding it into the table of contents
some of my data gets re-align every time i re-add it in within the QGIS Table of contents ( like a good 5-10 feet off). I have no idea what could be the cause, I may have the given layer in a ...
0
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0answers
55 views
Adjusting Spatial Accuracy of Ortho Imagery in ArcGIS Desktop?
I have about 35 square miles of orthorectified, high resolution, aerial imagery that is broken down into 620 individual tiff files. I have created a mosaic dataset of the imagery and I am working ...
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0answers
78 views
Accuracy of “on-the-fly” CRS transformation in QGIS [duplicate]
How accurate are the OTF transformations in QGIS (2.18)?
I created a 100m by 100m square polygon in a shapefile layer using a CRS of WGS84/UTM zone 14N (EPSG:32614). The project also uses the same ...
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0answers
235 views
Accuracy assessment in QGIS (Semi-Automatic Classification Plugin) without using random points?
i am using QGIS with the Semi-Automatic Classification Plugin. I already classified a Sentinel 2a scene by using an supervised classification approach. So I have trained areas all over the scene but I ...
1
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1answer
112 views
Unable to intersect a shapefile with a set of points
I have a set of 1000 urban points that I'm trying to intersect with a classification result to find the accuracy but I keep getting an error
"GEOS geoprocessing error: One or more input features have ...
