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Questions tagged [accuracy]

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

2
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0answers
70 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
76 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
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1answer
142 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
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1answer
47 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
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1answer
74 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
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2answers
382 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?
0
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1answer
20 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
123 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
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1answer
116 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
34 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
25 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" ...
0
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0answers
17 views

GNSS post processing under tree canopy

I am working on a project where we put a GPS on a tractor working in orchards. The tractor is driving slowly in the row (around 2-6 KPH). Many times, the trees canopy is braking the signal and we get ...
1
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1answer
101 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 ...
1
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0answers
79 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
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1answer
194 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
votes
2answers
97 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
64 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
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0answers
276 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
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1answer
261 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
35 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
46 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
58 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
149 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
104 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?
4
votes
1answer
1k 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
270 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
199 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
684 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
207 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
299 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
38 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
319 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
283 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
148 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
211 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
171 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 ...
1
vote
2answers
107 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
66 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 ...
2
votes
1answer
498 views

Accuracy assessment in R? [closed]

I would like to prepare a confusion matrix from decision tree module in R. Can anyone help me with the code that is needed for calculating user, producer and overall accuracy along with kappa ...
1
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0answers
320 views

How to validate high precision GPS systems location [closed]

I am currently working with a high precision RTK-GPS system which claims to be able to reach centimetre level accuracy, I am looking for a way to validate that it is actually reaching that precision ...
-2
votes
1answer
70 views

Are all remote sensing landcover/use classifications without ground survey scientifically invalid? [closed]

It is on the need of accuracy assessment of classification product. Land cover/use classification is a prominent analysis in remote sensing. Now the question is if I generate a landcover from LANDSAT,...
4
votes
1answer
60 views

How to do line based accuracy assessment with pyqgis

I would like to have a line based accuracy assessment between two line vector layers. For this it might an idea to create buffers around all lines of each layer and compute the % of overlay and % of ...
6
votes
3answers
3k views

Which is the most accurate method of measuring distance?

I aim to analyse the accuracy of the various methods of geodesic calculations (distance between two points on Earth)based on the three assumed models of Earth - flat, spherical & ellipsoidal. I ...
6
votes
1answer
154 views

Landsat ML classification: Apply accuracy measures to scenes without reference data?

I applied supervised maximum likelihood classification to a yearly stack of Landsat images (resolution 30m). The land cover classes are related to coniferous forest, i.e., forest, clear-cut, fire, ...
3
votes
3answers
100 views

Apply accuracy measures from partial area to the whole classified maps?

I applied supervised maximum likelihood classification to a yearly stack of Landsat images (resolution 30m). The land cover classes are related to coniferous forest, i.e., forest, clear-cut, fire, ...
5
votes
1answer
250 views

Accuracy Assessment for single date classification - possible to apply to classification without reference images?

I applied supervised maximum likelihood classification to a yearly stack of Landsat images (resolution 30m). The land cover classes are related to coniferous forest, i.e., forest, clear-cut, fire, ...
1
vote
0answers
165 views

Relative positional accuracy vs. registration error - what is the correct terminology?

I have several aerial orthorectified images that I am using for vector-based (points) change detection. I have calculated RMSE using sets of points on static landscape features in the images (e.g., an ...
2
votes
0answers
41 views

GPS accuracy for blind person O&M

I would like to be able to use GPS on my phone, in conjunction with an app, to enable O&M (Orientation and Mobility) support, on my device. I want the app to tell a blind person walking along a ...
3
votes
1answer
1k views

Accuracy assessment in R - Calculation of User Accuracy

I want to assess the accuracy of the land cover classes classified by supervised classification of Landsat images. As reference data I use the aerial photography. I sampled the classified Landsat ...