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Questions tagged [accuracy]

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

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0answers
17 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
21 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
30 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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83 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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49 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
30 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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56 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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0answers
24 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
15 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
55 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
62 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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24 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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25 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
127 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
98 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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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
38 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
70 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
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 ...
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2answers
110 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
670 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
85 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
118 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
840 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
41 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
262 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
194 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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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 ...
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0answers
33 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
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1answer
239 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
196 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
368 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
145 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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0answers
72 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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0answers
517 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 ...
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1answer
349 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
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1answer
38 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 ...
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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
74 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
219 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 ...
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1answer
111 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 ...
2
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1answer
2k views

Accuracy assessment using Google Earth Engine?

I'm using Google Earth Engine for Land Cover change detection, I would like to know whether we can generate Error Matrix (Accuracy Assessment) for a classified image in Earth Engine or not?
3
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1answer
2k views

What is the meaning of Altitude in EXIF of an image?

Currently I have some photographs​ captured by DJI, and in their EXIF I saw that it contains: GPS Altitude, Absolute Altitude, Relative Altitude, GPS Latitude, GPS Longitude. These images will be ...
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2answers
348 views

Correcting inaccurate position coordinates

How to project the journey onto the street? The black polyline is inaccurate GPS data received from a mobile device, which positions the user trajectory inside the buildings, when it was actually on ...
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0answers
268 views

How to perform accuracy assessment in eCognition?

I have already done the classification using Nearest neighbourhood, and how do I continue to complete AC with TAA?
3
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1answer
905 views

Confusion Matrix R

I'm having some problems to understand the result of my confusion matrix. Here is my case: I've run a classification (random forest) on a satellite image. To do so, I created 50 random points for ...
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0answers
304 views

define a precision accuracy QGIS project

How to define a precision accuracy of decimal places in QGIS project or where I use digitizing to add new features ? for example I have a point or polygon and true coordinates of vertex have to many ...
5
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1answer
386 views

Automated way of creating random points for accuracy assessment in QGIS?

I have created a land use land cover map using the SCP plugin of QGIS. I want to perform accuracy assessment of this classified image by creating 100 sample points for each class and importing them ...
4
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1answer
45 views

Accuracy assesment of an automatic line digitizer!

I have a polyline map which I extracted automatically and I want to compare it with another polyline map which I extracted manually in order to evaluate the accuracy of the automatic method. (my study ...
1
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1answer
442 views

GPS accuracy threshold standard

So obviously different applications would require different levels of accuracy, but I'm wondering if there's some standard threshold that the field typically determines to be "good" (or "good enough")....