Questions tagged [accuracy]
The degree of closeness of measurements of a quantity to that quantity's actual value
187
questions
4
votes
1answer
80 views
Loss of vector line accuracy when exporting from QGIS
I'm new to QGIS and having a little trouble understanding why my vector lines in QGIS look sharp and accurate but when I export and then import into MapBox, the line accuracy is reduced.
Vector end ...
0
votes
0answers
20 views
Accuracy assessment of RFclassificatiton in dzetsaka plugin QGIS
I tried random forest classification on dzetsaka plugin in QGIS to discriminate different plant species using sentinell(10m) and planet(3m) image. Classification is performed but i am confused about ...
0
votes
3answers
66 views
Accuracy of country shapefiles
I am working with a country shapefile for Pakistan, however it does not seem to be completely accurate. I wonder if this is an inherent limitation of shapefiles, or whether I could find an accurate ...
7
votes
2answers
160 views
GPS glitch causes 200 m circles around stationary position- Has anyone seen this before?
I am working with GPS data from public transport buses in a city in the UK. The data have very characteristic circles of approx. 200 m diameter at bus stops. I suspect that these are caused by an ...
0
votes
0answers
29 views
How to redesign confusion matrices from Ecognition with python and seaborn?
I am using eCognition manual classification as a baseline for performance comparison with other 3D classification methods. For each method, I am creating confusion matrices in python with sklearn and ...
1
vote
3answers
70 views
Finding applied transformation method and accuracy information when reprojecting layer in QGIS
When I load two layers with different CRS I'm prompted to choose a transformation method and there is a column indicating the accuracy (see image 1). I would like to know where the information as part ...
1
vote
0answers
24 views
Calculation GPS Accuracy based on known point
I have 3 GPS's that were on the same point for about an hour.
Each of them yield a fairly accurate position but not a complete accurate location (obviously)
I want to know how to calculate the best ...
0
votes
0answers
16 views
Accuracy Assessment-ecognition
When I did the accuracy assessment using classification stability or best classification result method in ecognition I got the output mean and std dev values in integer form not the decimal form . ...
2
votes
1answer
53 views
Better GPS accuracy in Android application
We are looking for ways to read higher GPS accuracy (less than 1 m) in our Android application.
We have tried with couple of mobiles having L1 frequency and supports GPS , GLONASS, Galileo etc but ...
2
votes
0answers
43 views
What is the best way to calculate the accuracy of GPS point measurements in relation to the road network?
I have a vector dataset containing GPS locations/points of different vehicles and a (polygon) road network dataset. Due to the inaccuracy of the GPS receiver, these gps points can deviate up to 10-20 ...
1
vote
1answer
62 views
How to exclude/eliminate invalid areas (such as NoData, cloud, water, etc) from raster so that it does not effect the accuracy assessment?
I have two classified raster (snow cover % 10-100) one is prepared from coarse resolution and another is from finer resolution. I am doing accuracy assessment and matrix calculation of snow cover %. ...
1
vote
0answers
36 views
QGIS SCP pulgin layer output
I use the plugin regularly and have already used every function. But I have often noticed that the output layers are not always intuitively understandable.
I googled on the topic and found no ...
2
votes
0answers
29 views
Landsat L1GS product processing to change detection analysis ready state
At high latitude area of Svalbard Norway, one can find Landsat 8 data processed to L1TP level. With previous Landsat missions, this is not the case. Landsat 7 data are processed to L1Gt level and ...
0
votes
0answers
156 views
Accuracy classification in Google Earth Engine
I'm trying to perform a supervised classification of a composite image from a Sentinel-2 time series. I'm using cart as classifier and a set of points as trainers. Once computed the classification I'm ...
1
vote
0answers
36 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 ...
0
votes
0answers
21 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 ...
2
votes
1answer
373 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
vote
1answer
69 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
votes
0answers
45 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
vote
1answer
84 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
vote
0answers
51 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
vote
0answers
36 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 ...
0
votes
0answers
280 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 ...
1
vote
0answers
70 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
113 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 ...
1
vote
1answer
95 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 ...
1
vote
0answers
1k 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 ...
1
vote
0answers
56 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 ...
0
votes
1answer
68 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? ...
1
vote
0answers
196 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
votes
0answers
30 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 ...
1
vote
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 ...
1
vote
0answers
78 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 ...
0
votes
1answer
103 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:...
0
votes
0answers
32 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
210 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
150 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. ...
0
votes
0answers
48 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 ...
1
vote
0answers
121 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
votes
1answer
3k 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
137 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
1k 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
114 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
229 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
1k 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
vote
2answers
43 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
vote
1answer
416 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
237 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
votes
0answers
43 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
vote
0answers
39 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" ...
