Questions tagged [accuracy]

The degree of closeness of measurements of a quantity to that quantity's actual value

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21 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 ...
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8 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 . ...
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1answer
46 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 ...
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42 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 ...
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1answer
58 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 %. ...
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33 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 ...
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25 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 ...
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85 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 ...
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21 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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20 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 ...
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1answer
248 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 ...
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1answer
53 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 ...
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43 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 ...
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1answer
67 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 ...
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43 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 ...
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35 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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158 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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58 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 ...
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1answer
82 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 ...
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1answer
78 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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723 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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53 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
57 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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166 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 ...
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29 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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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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72 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
91 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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29 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 ...
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1answer
173 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 ...
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1answer
137 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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45 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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97 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 ...
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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 ...
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2answers
130 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 ...
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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 ...
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1answer
104 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 ...
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1answer
196 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 ...
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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?
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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 ...
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1answer
369 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({ ...
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1answer
226 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 ...
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42 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 ...
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37 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" ...
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1answer
385 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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304 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 ...
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1answer
620 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. ...
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2answers
174 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 ...
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76 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 ...
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627 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 ...