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

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7
votes
1answer
378 views

How to store Large Raster Images of Equipotential Surface Generation Using Monte Carlo Simulation?

I have a large (1GB+) raster that I am using as the base for the generation of an equipotential surface. This is to assess the accuracy of DEMs derived from another source. In situ observation is ...
1
vote
0answers
16 views

Is there a well-known way to compare the relative accuracy of 2 latitude/longitude results?

I have 2 geocoding results (in latitue and longitude) for a given address from different services. I'm interested in describing the results in relation to one another in terms of relative accuracy and ...
0
votes
1answer
55 views

Remote sensing accuracy assessment - McNemar`s Test

I would like to know how you determine the f12, f21 parameters for use in the McNemar`s test when for example I have two confusion matrices such as below: (where f12 = number of cells misclassified ...
1
vote
0answers
25 views

Can typical Meets and Bounds (angles and distances) drawings be accurate in QGIS?

I’ve been working with parcel boundary shape files (.shp), standard satellite imagery, and Meets and Bounds (angles and distances) site maps / legal descriptions for a few weeks. Wondering if those ...
0
votes
1answer
619 views

ENVI 5.2.1 How to do an Accuracy Assessment using test data from a shapefile

ENVI 5.2.1. From a .tiff image (4 bands) I created a Supervised Classification Maximum Likelihood .dat file. Now I want to perform an Accuracy Assessment using test data from a shapefile. I've tried ...
0
votes
0answers
14 views

Proper Tool for Creating a 3x3 Window for Cluster Sampling in Accuracy Assessment?

I'm using a cluster sampling scheme for an accuracy assessment of the 2011 National Land Cover Dataset (spatial res of 30m). I'm using Google Earth Pro for my reference data spatial res of 15m). So ...
0
votes
1answer
34 views

Creating a Grid For Raster When Measuring Land Cover In Accuracy Assessments

I am assessing the accuracy for the 2011 National Land Cover Map (NLCD). Each pixel for the NLCD measures 30m x 30m. For my reference data, I'm using two sources: 1) Google Earth (~20 m ...
0
votes
0answers
31 views

Basemap (Matlibplot) not plotting GPS WGS84 coordinates accurately

I have a list of lat,lon coordinates from Flickr pictures taken in Sydney (see here) When I plot these points on google maps, the locations are correct. However when I use my Basemap the results are ...
2
votes
1answer
2k views

How is Precise Point Positioning (PPP) exactly done?

I am looking for a positioning accuracy that is higher than normal consumer-grade GNSS receiver (mostly GPS/GLONASS hybrids with +- 5m precision). I came across RTK with dual receiver setup (base ...
3
votes
0answers
124 views

How to measure RTK accuracy of a moving vehicle?

I am currently working with tractors using a RTK enhanced automated steering system. One of the biggest problems is that even RTK can have a inaccuracy of 2cm. This can be too much for some possible ...
3
votes
2answers
89 views

What's the accuracy of Web Mercator EPSG:3857?

Are there any references on the accuracy or (min/max/avg) error of Web Mercator when it comes to e.g. distance calculations? (For the sake of completeness, I haven't found any reference to the ...
5
votes
1answer
52 views

Pacific-wide Projection for distance?

I have a data set of ~3500 points located across the Pacific Ocean, and am looking to measure the distance from each point to it's nearest coastline to identify the "host" country. I had originally ...
6
votes
2answers
107 views

How does a GPS device determine bearing?

Following a discussion on Math and this particular comment, I am wondering how a GPS receiver determines its bearing. As I understand it: GPS is not a directional system, thus bearing can only be ...
4
votes
1answer
82 views

Find out if overlaying polyline matches polygon centerline in qgis

I have a polygon and a polyline and I need to find a scientific way of how close that polyline is to the actual polygon centerline. Is there any way of doing this in qgis? Any extensions, models, ...
12
votes
3answers
1k views

GPS Elephant Tracking: Utilizing A-GPS, WAAS, DGPS and Understanding HDOP, NSAT, and ZDA

*I'm using a GPS data logger (qstarz bt-q1000xt) to track the movement of zoo elephants, and I have a variety of technical questions. I've had limited success receiving answers from the vendor. You ...
1
vote
1answer
92 views

Average stationary position with GPS

Is it possible to average a stationary position with a GNSS (GPS, GLONASS...) with a centimeter accuracy without external corrections (like differential or RTK)? If so, how long does such averaging ...
21
votes
6answers
5k views

How correct is the “Accuracy” value given by GPS devices?

I have a Garmin Forerunner 305 and a Google Nexus One Android phone. From the GPS on both these devices I can get a "Accuracy" value that is usually between 6-20 meters. How much can I trust this ...
0
votes
1answer
407 views

Accuracy of GPS and HDOP

Given a handheld GPS with an accuracy of roughly 2 meters (verified through field tests) and an observation with an HDOP of 1.2, the accuracy of that one observation should be within 2 meters X 1.2 of ...
3
votes
3answers
82 views

What view of sky is required for RTK GPS

When using RTK or differential GPS technologies, considering the Base has a clear unobstructed view, what view of the sky is required to be able to get an accurate fix with the rover when is moving ...
2
votes
2answers
3k views

What class/types of smartphone chipsets support GPS, A-GPS, GLONASS AND have extended kalman filtering?

I've been testing several Android phones (all running Android 4+) Sony Xperia T, Moto G, Nexus and HTC 1 which are all giving decent tracks (all of which use GPS/GLONASS) However we are also using ...
23
votes
5answers
37k views

What is the maximum Theoretical accuracy of GPS?

I was talking with a potential client, and they requested that we plot some points with GPS, with a maximum (or should that be minimum?) accuracy of 2 m. This is an area with no WAAS, and I was under ...
9
votes
2answers
7k views

Low-cost centimeter-level accurate satellite positioning (GNSS/GPS) [closed]

I am looking for a low-cost (< US$500) GNSS/GPS setup with a centimeter precision without much HW hacking. I am not able to produce my PCB or do any soldering (though I would do that if there is no ...
2
votes
1answer
50 views

Accuracy calculated by GPS

I found a lot of pieces of an answer to this question, but no complete and good one. How does a GPS System calculate it's own accuracy at the moment? Where does it get the known position to ...
0
votes
0answers
65 views

Using shapefiles as a reference for accuracy assessment in ecognition

I classified my project and got an esri shapefile with points in it. Those points are hand made samples with the right class assigned to them. Now I need to use those samples to check my own ...
1
vote
2answers
65 views

Collector blue accuracy ring- what does it show?

What, definitively, does the blue accuracy ring show in Collector. In the field it always seems too large to represent the accuracy that the GNSS app is stating (ie 50cm – 1m). The blue ring seems to ...
1
vote
1answer
87 views

Elevation adjustment DSM using Ground control points

is there any possibility to improve the vertical accuracy of a given satelite DEM/DSM by using exact measured ground control points? And if so, which software is recommended?
3
votes
1answer
1k views

Google Earth, Google satellite, and Bing aerial accuracy

Does anybody know the accuracy of Google Earth, Google satellite, and Bing aerials, and at what scale? I think that you have different/better accuracy if you have subscribed to their professional ...
5
votes
1answer
450 views

How to compare two sets of points in QGIS?

I have two point layers with XYZ data; one set are points measured in the field and the second set is a Lidar data set. I want to check the accuracy of the Lidar in comparison to the measured data. ...
1
vote
1answer
62 views

Checking the registration accuracy of already-orthorectified images

I acquired several Landsat 5-8 images corrected at Level 1T. I also have aerial ortophotos of the same area. From a visual assessment the co-registration between the images seems good, but I need to ...
2
votes
2answers
108 views

Is this distribution of GPS positions caused by multipath distortion?

I have some GPS points that are close to where they should be, but not nearly close enough (horizontal precision is around 10 meters). Looking at the positions which comprise these points (there are ...
37
votes
2answers
4k views

How accurate is approximating the Earth as a sphere?

What level of error do I encounter when approximating the earth as a sphere? Specifically, when dealing with the location of points and, for example, the great circle distances between them. Are ...
1
vote
1answer
152 views

Measurement of accuracy for image segmentation of land cover image in python

I have a land cover image and I segmented it using K-means clustering algorithm. Now I want to calculate the accuracy of my segmentation. How do I do that? I have read about dice similarity ...
1
vote
2answers
72 views

Geocoding Adresses with varying levels of reporting accuracy?

I am trying to geocode a database that has, I'll call it "4 tiers", of address types. They are: Numbered Street (e.g. 506 Taproom Way) Cross-street (Happy Road $ Jubilant Blvd) Hundreds Block (500 ...
175
votes
5answers
138k views

How to measure the accuracy of latitude and longitude?

I am very new to GPS stuff. Suppose I have latitude and longitude as 19.0649070739746 and 73.1308670043945 respectively. In this case both coordinates are 13 decimal places long, but sometimes I also ...
2
votes
1answer
517 views

How to calculate RMSE of geographic coordinates?

I've been working on my project and I stumble upon how I can calculate the Root Mean Square Error (RMSE) of geographic coordinates. What I have is a derived coordinates from processing LiDAR data ...
2
votes
1answer
338 views

Relationship between contour interval and spatial resolution of a generated DEM

If I have contour lines with interval say 10, 5, or 2 (etc.), and I generated a DEM from them, what is the relationship between between the contour interval and the resolution of the DEM? Irrespective ...
1
vote
1answer
45 views

Transfer from Android phone to Windows OS truncates lat long

I am clicking GPS enabled pictures of sites which are less than 500 metres apart through Android based Samsung ACE Duos phone. I later use Google Earth on my Laptop to view these geo tagged pictures. ...
21
votes
6answers
4k views

Is GPS more accurate on specific hours of the day?

I have heard that the GPS system is more accurate, and less accurate on some specific hours on the day. If this is true, how can I get the information on when GPS is more or less accurate at my ...
13
votes
2answers
1k views

ArcGIS Buffer accuracy problem?

Once again I encounter something very strange with ArcGIS. I perform a buffer analysis on one side of a polyline. There seems to be a serious accuracy problem and I can't figure out what the cause is. ...
0
votes
0answers
238 views

ERDAS file not recognized as ERDAS Hierarchal File Architecture (EFHA)?

I am trying to do an accuracy assessment in Erdas using "user defined ground control points" (I collected the GPS points myselfin the field using a handheld GPS). However, when I load the thematic ...
0
votes
0answers
80 views

How to randomly generate 3 X 3 pixel window/grid size in ArcMap?

I have a raster image in ArcMap and I want to assess the accuracy of my raster image with a reference image. So, I need to randomly generate a bunch of (i.e 50) 3 X 3 pixel window/grid size from my ...
14
votes
2answers
2k views

How much sense does it make to average (lat,lon) samples in order to increase 2D accuracy of a GPS location?

Several GPS applications, like this one, or this one, acquire multiple (lat,lon) samples of a given location, assuming that the GPS unit is not moving, and then take an average of the samples in order ...
1
vote
0answers
448 views

Collector for ArcGIS PDOP and GPS collection configuration settings

My company just acquired a Geneq SXBlue II GPS receiver to pair with an iPad and the Collector for ArcGIS app. The functionality is awesome and loved by everyone, but since we have biologists on our ...
1
vote
0answers
98 views

How to select random objects in eCognition?

I classified a Landsat image in eCognition and now I want to select random objects so that I can compare their class to ground-truth data and perform the accuracy assessment. How can I do this in ...
1
vote
1answer
84 views

Why does the undefined “ghost classes” arise during supervised classification in ERDAS IMAGINE?

After a supervised classification in ERDAS IMAGINE I have some undefined "ghost classes" in the attribute table. Also have a look at this youtube video at about 7:12. I'm wondering why they arise and ...
0
votes
1answer
159 views

Benefit of DGPS for relative accuracy and speed measurements for receivers close-by each other

Consider that we are interested only in the speed and relative position accuracy of GPS receivers (i.e. their absolute try position on earth is NOT important). These receivers are all in a 90m x 90m ...
3
votes
2answers
252 views

Accuracy assessment using polygons as reference data as against point data?

Is it possible to do accuracy assessment using polygons as reference data as against point data? I have field-identified polygons as data for training and reference (from a forest-agri mosaic) that ...
2
votes
0answers
466 views

How to use QGIS Accuracy Assessment plugin? [closed]

I am new user and i want perform accuracy assessment in qgis. I have 1 classified map and another for validation. I have installed the plugin. what am i doing after? Plugin: ...
3
votes
2answers
67 views

Compensating lat/long offsets after conversions

In my application I am doing conversions between two different formats of data. First format is a simple one containing NE and SW coordinates for a given rectangular area: area = { "sw": { ...
2
votes
1answer
104 views

resampled thematic map accuracy

I've generated a map of ecoregions based on some environmental data using a semi-supervised classification where I combined a statistical clustering with random forests to generate my map. I created ...