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142

Accuracy is the tendency of your measurements to agree with the true values. Precision is the degree to which your measurements pin down an actual value. The question is about an interplay of accuracy and precision. As a general principle, you don't need much more precision in recording your measurements than there is accuracy built into them. Using too ...


50

The Wikipedia page Decimal Degrees has a table on Degree Precision vs. Length. Also the accuracy of your coordinates depends on the instrument used to collect the coordinates - A-GPS used in cell phones, DGPS etc. decimal places degrees distance ------- ------- -------- 0 1 111  km 1 0.1 11.1 km ...


12

It depends on what you mean by 'Universal Coordinate System'. If you wonder whether most Professionals understand Latitude and longitude, well in that case it is pretty much universally understood. But if you ask, whether it is used by everyone, then the answer is a resounding, No. There are many reasons why people use projected coordinate systems instead ...


10

I've answered this question in passing while answering another of your question. The Greenwich Observatory was defined as a prime meridian, based on the observations by the astronomer Sir George Airy in 1851. London was selected as the official prime meridian for international maps by the International Meridian Conference in 1884. When you use a GPS, by ...


8

The principal radius of the WGS84 spheroid is a = 6378137 meters and its inverse flattening is f = 298.257223563, whence the squared eccentricity is e2 = (2 - 1/f)/f = 0.0066943799901413165. The meridional radius of curvature at latitude phi is M = a(1 - e2) / (1 - e2 sin(phi)^2)^(3/2) and the radius of curvature along the parallel is N = a / (1 - e2 ...


8

Try this formula (assuming your source is WGS1984, if not then you'll need to adjust the ellipsoid used by the second line): area = rad(x2 - x1) * (2 + sin(rad(y1)) + sin(rad(y2))) + rad(x3 - x2) * (2 + sin(rad(y2)) + sin(rad(y3))) + rad(x4 - x3) * (2 + sin(rad(y3)) + sin(rad(y4))) + rad(x5 - x4) * (2 + sin(rad(y4)) + sin(rad(y5))) area = abs(area * ...


8

Seems to be http://en.wikipedia.org/wiki/UN/LOCODE Coordinate syntax explained in http://www.unece.org/fileadmin/DAM/cefact/locode/Service/LocodeColumn.htm#Coordinates 1.10 Column "Coordinates" This column contains the geographical coordinates (latitude/longitude) of the location, if there is any. In order to avoid unnecessary use of ...


8

A lat lays flat. Can't think of a matching one for longitude.


8

I always remember Longtitude as being "Long", where the lines do not change in length, and circle the globe. Also, Latitude being lateral, i.e. sideways


6

Here's a Python function that creates a memory layer containing a line at the specified latitude. You call it using createLatitudeLayer(latitude=-23), for example. You can specify which CRS the layer should use by specifying targetCrsEPSG=<EPSG code>. You can also specify how many points to use for creating the line, by setting numpoints=<number ...


6

The trick of remembering latitude as 'ladder'tude always helped me. Think of a ladder standing up and the rungs of the ladder representing the E-W latitude lines.


6

One could use either kind of latitude to locate points on the WGS 84 ellipsoid (used by the NED) or any other ellipsoid, but "everybody knows" that the values will always be given as geodetic latitudes. However, it is surprisingly hard to find an authoritative statement to that effect! Before we go on, it helps to understand that although a datum like the ...


5

Looks like ogr2ogr has support for exactly this problem. The below is copied directly from that page: How do I flip coordinates when they are not in the expected order The EPSG has a recommanded order for geographic SRS where the coordinates tuples of a geometry must appear in the (latitude, longitude) order, whereas most GIS will properly display such ...


5

I'll try to explain it in different terms: Earth's equatorial circumference is about 40,000 kilometers (25,000 miles). A latitude/longitude value breaks that distance up into 360 degrees, starting at -180 and ending at 180. This means that one degree is 40,000 km (or 25,000 miles) divided by 360: 40,000 / 360 = 111 25,000 / 360 = 69 (So, one degree ...


5

Simply create a text file with this content: id;wkt 1;LINESTRING(-180 -23, 180 -23) and use Layer -> Add delimited Text Menu entry with semicolon as delimiter and EPSG:4326 as CRS. For meridians, it is better to end the line at 89° when using EPSG:3857: id;wkt 1;LINESTRING(7 -89, 7 89)


5

Unless I'm misunderstanding the question, the shape's .extent property is all you need. with open('out.txt', 'wb') as out_text_file, arcpy.da.SearchCursor('path_to_data', ('msa', 'SHAPE@')) as cur: print >>out_text_file, "msa min_lon max_lon min_lat max_lat" for row in cur: msa, ext = row[0], row[1].extent print ...


5

As whuber said, they are lat-long, but in decimal minutes. Those are very uncommon, but in a sense, useful, units for geographic coords. Lat and long at Silverstone: 52.065567 and -1.020708 (decimal degrees) 3123.93402 and -61.24248 (decimal minutes) 1 degree = 60 minutes


4

If you're working in Ubuntu, you could use this in a shell script: To get longitude like 81°5.8' (degree and minutes from code in d,m,s): tmp0=`echo 081054800 | cut -c2,3` tmp1=`echo 081054800 | cut -c5` tmp2=`echo 081054800 | cut -c6,7` tmp3=`echo "scale=2; $tmp2/60" | bc -l` echo $tmp0 $tmp1 $tmp3 | awk '{ print $1"°"$2$3"'\''" }' which gives: ...


4

Please check out following links For GPS Locations (Flights): http://www.flightradar24.com/data/ http://www.radarvirtuel.com/ For GPS Locations (Ships) http://www.marinetraffic.com/ais/default.aspx?centerx=30&centery=25&zoom=2&level1=140 For Weather: http://openweathermap.org/wiki/API/Leaflet_library and http://openweathermap.org/weather ...


4

There is nothing in your Question to suggest that you need to perform a conversion. Instead, I would try: point = osgeo.ogr.Geometry(osgeo.ogr.wkbPoint) point.SetPoint(0, 112.73091137, -7.2377761) The original values look like they are from a projected coordinate system whereas you appear to be receiving Twitter data in a geographic coordinate system but ...


4

The short answer is: there was a historical shift between the first global datum and the Greenwich meridian; and it continues to move (slowly) because of continental drift. You can find more detailed information on this site In the late 1950s (under the auspices of the US Navy), the Applied Physics Laboratory (APL) of the Johns Hopkins University began ...


4

I have done this before using forward azimuths, here is a link that has descriptions and algorithms that may be helpful: Inverse/Forward Utilities A forward azimuth calculates a new point that is a specified distance and compass bearing from a starting point. The basic idea is that you have a point in Lat/Lon and you calculate a series of forward azimuths ...


4

From 3rd grade: lOngitude goes nOrth-sOuth


4

Are the longitude and latitude values in separate fields? Because the Convert_Decimal function requires a single value. After trying this myself, I think you were trying to convert the DMS values to DD in-place. That is, in the same column. Instead, use the script in a new column, referring to the one you want to convert. See image below where I have a DMS ...


3

Check NOAA's GSHHG (Global Self-consistent, Hierarchical, High-resolution Geography Database). The database is constantly being updated and maintained (latest update since Im answering this Q: July 1, 2013) GSHHG is: a high-resolution geography data set amalgamated from two data bases in the public domain: World Vector Shorelines (WVS) and CIA World ...


3

There is no meaningful way to link "time the GPS is on" with a particular precision level. The accuracy is driven by many factors ranging from the characteristics of the hardware (especially the antenna) through to atmospheric conditions and GPS satellite constellation configuration. A reasonable approach (using information you can get from most receivers) ...


3

If I understand well, you have your data in a Coordinate System (from your description, probably geographic one), and you want to see\capture coordinates in a different system. In QGIS you can do the following: Option 1 -Set you Project to the desired coordinate system Make sure you set the correct CRS for your layers using right-click over the layer ...


3

It's clear that it's not necessary to shift the projection, but the data. Using GDAL >= 1.10.0 compiled with SQLite and SpatiaLite: ogr2ogr russia_shifted.shp world.shp -dialect sqlite -sql "SELECT ShiftCoords(geometry,360,0) FROM world WHERE CNTRY_NAME='Russia'" where shiftX = 360 (degrees) and shiftY = 0. UPDATE: here's the whole workflow... Clip ...


3

Welcome Lucy -- your question is a little bit unusual for this site, which mainly caters to people who use geographic information systems professionally or in research. I found it surprisingly hard to google up a site that has a concise history and comparison of navigation tools over time. However, I think the Smithsonian Museum's Time and Navigation site ...


3

The QuickWKT plugin is very useful for putting temporary lines, points or polygons on the map; a trifle buggy but works. Install it and you'll get a new toolbar button 'WKT' - click it and you are given a dialogue with space to paste a WKT string, and a drop-down menu to load examples of WKT strings. I am having trouble with adding a LINESTRING when it ...



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