Questions tagged [accuracy]
The degree of closeness of measurements of a quantity to that quantity's actual value
226 questions
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Higher accuracy formulas for Direct and Inverse problem
I am having an issue with the accuracy of the formulas for the direct and the inverse problems given at the National Geodetic Survey website.
Note: I use the full formulas, including the terms that ...
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Maximizing accuracy with RTK/DGNSS
I have an Ardusimple simpleRTK2B and an SBG Ellipse D. I am trying to construct a rover-base station kind of system where the SBG Ellipse D is located on the Rover and simpleRTK2B on the base station. ...
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Improving point loaction accuracy after an RTK survey
I have recently collected the location of a number of points using RTK with base and rover GNSS recivers (Emlid RS2). My base station was not placed over a known point, meaning the base postion was ...
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Calculate the error distribution of fractional abundance values between classes (a spectral mixture analysis issue)
I am trying to estimate the distribution of the under- and overestimation errors that I found in the outputs of a spectral mixture analysis (SMA), i.e. abundance fractional maps (AFM).
Specifically, ...
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Edit feature without losing GPS data in QField
I use QField to collect data entered manually in the field. But also internal GNSS data (horizontal and vertical precision).
In the QGIS form I save the default values: @gnss_horizontal_accuracy and @...
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OpenStreetMap Polygon data accuracy checking
I was wondering whether there is a method or exercise I can do to check the accuracy of building polygons sourced from OpenStreetMap (https://download.geofabrik.de/)?
Of course when I layer the ...
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Converting vectorization (raster to vector) with small steps in values in QGIS
I have a raster file that contains water depths in m. The water depths are the only attribute and should be transferred to the vector layer.
The raster files have a cell accuracy of 1m x 1m. I would ...
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Why if I spoof the position with GNSS Analysis MATLAB Google code,I get a spike of horizontal speed but it continue to be active while should be const
I'm using this GNSS Analysis Matlab Google code
to analyze the measurements performed via GNSSLogger app.
I was initially in Palermo,Sicily and tried to spoof to Rome. I get this
Horizontal speed ...
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Finding accuracy of water indices
I have calculated the water indices NDWI, MNDWI, WRI, and applied binary thresholding. I want to find out the accuracy of these indices.
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File not found, no such file or directory in GEE python
I follow step by step in :
https://geemap.org/notebooks/33_accuracy_assessment/#split-training-and-testing
When the step to download confusion matrix, there is error. I type the code :
import csv
...
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Buffer accuracy in virtual layer differs from accuracy in PostGIS view
I used virtual layer query to create a buffer for a point as this allowed me to transform its SRID using the PostGIS function ST_Transform, which is not possible with the ready-to-use Buffer algorithm ...
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Accuracy assessment of unsupervised clustering - GEE
I have clustered my map on the basis of NDVI values using an unsupervised approach. I don't have the labels. However, I do have the cluster IDs that were automatically assigned.
How do I assess the ...
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Android GPS accuracy (2 m) is greater than nominal accuracy
I read in several posts and websites that public GPS signal to smartphones has an accuracy of around 5 m, and that civilian signal accuracy is 100 m. Some other posts mentioned accuracy of c. 2 m and ...
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How to calculate accuracy of a calculated (predicted) coordinate (latitude, longitude)?
Given GPS data that consists of:
Latitude
Longitude
Bearing (degrees)
Speed (meters per second)
Accuracy (radius of the circle around the coordinate where true position can be found with 68% chance, ...
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Calculating distance discrepancy: EPSG 3112 Projection VS GeoDesic (Karney), is ~0.5% difference normal?
I have lat-lng coords in EPSG:4326, and I'm calculating the distance between them (in metres).
Since these are in Australia (and Australia wide, therefore no specific MGA zone projections), I'm using ...
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Accuracy Assessment of NDWI - GEE
I have applied NDWI (Normalized Difference Water Index) on years: 2018, 2019 and 2020 to extract the water bodies. Then I used MCD12Q1.061 MODIS Land Cover Type Yearly Global 500m product for the year ...
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Low accuracy for addition of more predictor bands in Random forest classifier
Hi there Im working on a project for estimation Above ground Biomass in hilly terrain for mature forests and asscessing accuracy of different classifiers availiable in GEE such as Random forest and ...
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Accuracy assessment on multiple classified images
I am attempting to compare the accuracy of multiple different classified images I have created from a single raster. Basically, I want to avoid having to input 'ground truth' values for each accuracy ...
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Classification map in GEE does not correspond to accuracy results
I have this script in GEE that has worked successfully before for LULC mapping (with 8 classes). I used this script for mapping solar panels (2 classes: solar & non solar). The accuracy results ...
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How to find the standard deviation in GPS measurement of latitude and longitude?
Let's say my GPS configuration is said to have a precision of 10 meters. I have taken this as the standard deviation in the GPS measurements. But the measurements that come from GPS are latitude, ...
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Tell GeoPandas the number of significant figures to use when writing GeoJSON geometries
I have a GeoDataFrame gdf. I write its contents to a GeoJSON:
gdf.to_file("example.geojson")
which works. However, each geometry is specified to 16 significant figures, which is an overkill ...
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Increasing accuracy with RF classifier in GEE
I am doing a supervised classification using RF classifier in GEE. However, the accuracy that I am getting is not exceeding 0.67, even if I increase the training sample or no. of trees in my ...
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Why recommended transformation is not the most accurate in QGIS?
When I am prompted for a transformation to use in QGIS, the recommended/default option (in green) is the least accurate one. In my case, QGIS recommends a transformation with an accuracy of 6m when ...
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HUGE latitude error from iPhone 4s
2015 April 15, I wandered around Little Rock, Arkansas, on bike, taking pictures with an iPhone 4s. Cloudy day, though some photos show shadows. Here are some of the metadata from three consecutive ...
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How can I calculate the midpoint between three points using accurate variables like Horizontal accuracy and HDOP
I have three (3) points with the following fields:
X
Y
Horizontal Accuracy
Vertical Accuracy
PDOP
HDOP
VDOP
And I would like to calculate the midpoint between these three points, using accurate ...
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How to compute theoretical GPS accuracy?
I'm a student and I am working on a GPS-like system.
I have implemented a few algorithms (Newton-Raphson, Bancroft, ...) and I would like to compare them.
Basically, I have a constellation of ...
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How can I improve the accuracy of a DEM using surveyed points?
I have a DEM and many surveyed points in the area. The survey points have centimeter accuracy. The difference between the DEM to the actual height ranges from -20cm to +20cm. It is not a uniform ...
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359
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OpenLayers vector accuracy in EPSG:3857 projection
I'm working on a web mapping solution that stores data in PostGIS with EPSG:4326 projection. Everything seems to be good until last week. My customer loaded two shapefiles that some parts are ...
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Set marker size equal to GPS accuracy with variable opacity?
I have an exported collection of iNaturalist observations which have latitude and longitude values, but also report the GPS accuracy in meters. This data is in the form of a csv file.
The accuracy ...
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Sudden change in altitude during measurement with GNSS
We work For some time now we have been working with QField and the GNSS receiver from Emlid. We get the accuracy via bluethoot from the receiver to QField. Lately, however, the measurements have been ...
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Evaluating classification accuracy and the result of kappa test in Google Earth Engine
I am trying to check the efficiency of the classification. The classification accuracy and kappa test for 2020 are 0 while for 2000 is 1. I am just not able to put my finger on what is incorrect as ...
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Can I get ~1cm accuracy with a 2.5m accuracy GPS module and RTCM/NTRIP data after post processing?
I'm a new on this, so I have a subscription to a RTK? service that sends correction data (RTCM/NTRIP) over GPRS/UMTS (you get a SIM card with the subscription)
I'm also having a Rover of around 2mx1....
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What does the coordinate values represent when using WGS 84 / Pseudo-Mercator (EPSG:3857)?
I have been using QGIS for a couple of weeks now, mostly for data collection in my research project. Currently, I'm trying to plot these points,
in a graph similar to this one (but in kilometers),
I ...
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How to calculate 2 sigma circular approximation for GNSS positional accuracy?
I'm using gpsd application and I get the positional accuracy related data, i.e.,
semi-major axis accuracy semi-minor axis accuracy and semi-major axis orientation of the error ellipse. These values ...
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Under which condition(s) does geopositioning precision infer accuracy?
I am not sure whether this is the right forum for this question but I reckon that since it gathers experts in GIS, the odds of someone having valuable insights is higher than anywhere else. So here's ...
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How to interpret gpsd TPV accuracy info
I want to understand the epx (Longitude error estimate in meters, 95% confidence) and epy (Latitude error estimate in meters, 95% confidence) values in a gpsd TPV packet.
If I have data like this
{
&...
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Accuracy of Google maps/HERE maps
According to this article in https://junipersys.com/support/article/6614, I have a basic understanding of the accuracy of GPS data.
Through calling Google Maps/HERE Maps API, we are able to receive ...
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Controling accuracy of polygon data using ArcMap
I have a question regarding polygon data. I implemented "Calculate geometry" and the new column includes the area of interest to ha. The problem is with the accuracy of the data. The site ...
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Is it possible to achieve sub-meter accuracies with a smartphone, without using an external GNSS-receiver?
I am currently working with QField on my tablet (Samsung Galaxy Tab S5e) and my smartphone (Samsung Galaxy A40). Since the positioning accuracy on my devices is rather low (absolute best case ~3m on ...
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Single numbers for accuracy and resolution for vector and raster data?
This question is meant as a modelling question, not having to do with particular data formats. It was edited to better separate spatial accuracy and resolution (precision).
In order to make the ...
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Accuracy of latitude and longitude based on decimal places [closed]
After reviewing various information regarding accuracy of latitude and longitude for specific decimal places, I have a question regarding the information that many have posted, such as in Measuring ...
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Save GNSS accuracy for each vertex of polygon/line feature in QField
In QField it is possible to save positioning information in point features through expression variables like @position_horizontal_accuracy or @position_number_of_used_satellites. The explanation is ...
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How to calculate the accuracy of georeferenced aerial images in meters if the mean error is in pixels?
I have scanned aerial images taken shortly after WWII and have to georeference them and calculate the mean error. I use the Projective transformation so the error after transformation is shown in ...
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How to improve the horizontal and absolute accuracy of UAV layer
I am working with two digital elevation model data sets: LiDar and UAV DEMs. Both flights were conducted in the same location along a coastal shoreline showing the intertidal area with lots of bare ...
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QGIS 3.14.15: is there a build in option for storing additonal quality data from trackpoints captured with DGPS antenna
I'd like to use QGIS for collecting datapoints in field. Due to the 'GPS information module' it is no big deal to connect the R2-Antenna via Blutooth-link and read the NMEA stream.
As far as I figured ...
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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 ...
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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 ...
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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 ...
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320
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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 ...
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467
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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 ...
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