Questions tagged [accuracy]
The degree of closeness of measurements of a quantity to that quantity's actual value
161
questions
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37 views
How can I compute confusion matrix using Python
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
18 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
14 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
40 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
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1answer
49 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
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0answers
19 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
23 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
105 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
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1answer
64 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
18 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
34 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
59 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
1k 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
101 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
466 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
68 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
102 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
722 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
39 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
195 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
173 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
37 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
32 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
187 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
154 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
300 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
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2answers
121 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
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0answers
68 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
455 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
votes
1answer
340 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 ...
0
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0answers
51 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 ...
1
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0answers
71 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
211 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
110 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
votes
1answer
1k 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
votes
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 ...
1
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2answers
316 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 ...
1
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0answers
249 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
votes
1answer
854 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 ...
1
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0answers
277 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
votes
1answer
365 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
votes
1answer
42 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
400 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")....
1
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0answers
344 views
Accuracy assessment in QGIS
I am using QGIS and the SCP plug-in to classify a sentinel 2 image.
As for the reference shapefile my point layer, is a vector point layer containing the names of crops, which were used in creating ...
5
votes
3answers
164 views
How to check accuracy of Roads
We've been doing QA work on a roads dataset and I realized that many of the roads don't overlay correctly with their counterparts in Google Maps or OSM.
Currently we compare our roads with the ...
1
vote
1answer
259 views
Accuracy Assessment in Erdas Imagine 2015
I'm trying to achieve accuracy assessment in Erdas, but I've faced some difficulties due to my lack of knowledge about it.
I've finished an object based classification in eCognition, but whenever I ...
1
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0answers
327 views
Calculate Positional Accuracy of Feature with CE/LE Values
I would like to report the predicted positional accuracy of features that have been extracted from WorldView imagery. I have predicted horizontal accuracy and vertical accuracy values (CE90/LE90) for ...
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2answers
118 views
Correcting commercial grade GPS data to 2 meter accuracy in RT?
I have a set of rovers with commercial grade GPS boards (Adafruit Ultimate GPS Breakout). They send their uncorrected data to the central server. There, before recording each position in the database, ...
2
votes
1answer
70 views
Measuring positional accuracy of points in QGIS?
I am looking for an approach to calculate and assess the positional accuracy of POIs in QGIS.
I have two layers that show the locations of supermarkets:
One is from a commercial database and the ...
