I use 2 ways if calculating distance between coordinates, difference between them is quite big (more than 400 m). Do you know why? And which one of all ways of calculating is the most accurate?
1st:
DECLARE #source geography = 'POINT(53.9202690124512 14.2586479187012)'
DECLARE #target geography = 'POINT(53.8970128 14.2387088)'
SELECT #source.STDistance(#target)
2nd:
SELECT geography::Point(53.9202690124512, 14.2586479187012, 4326).STDistance(geography::Point(53.8970128, 14.2387088, 4326))
geography::Point expects the latitude and longitude to be passed in that order. WKT's POINT expects longitude and latitude to be passed in that order. See the results of:
DECLARE #wkt_source geography = 'POINT(53.9202690124512 14.2586479187012)'
DECLARE #wkt_target geography = 'POINT(53.8970128 14.2387088)'
select #wkt_source.STAsText() as wkt_source, #wkt_target.STAsText() as wkt_target
declare #point_source geography = geography::Point(53.9202690124512, 14.2586479187012, 4326)
declare #point_target geography = geography::Point(53.8970128, 14.2387088, 4326)
select #point_source.STAsText() as point_source, #point_target.STAsText() as point_target
So you will need to swap one or other around to get consistent results (depending on which lat/lng is correct).
Related
I have a polygon WKT and turning it into a geography and am presented with two polgyons, but where they overlap there is a void.
I am trying to find markers that exist in any polygon in the string (lat long intersects). The issue is that this void that is created I am not being delivered markers that exist there when it is required.
IF OBJECT_ID('tempdb..#customPolygon') IS NOT NULL DROP TABLE #customPolygon
CREATE TABLE #customPolygon (geog GEOGRAPHY)
[![DECLARE #customPolygon geography = 'MULTIPOLYGON (((-122.31260682058497 41.7828672412252, -122.66803538233832 41.74189213171878, -123.0157152218382 41.67409631073075, -123.35191487435746 41.58021595697532, -123.67306979164175
41.461266240272025, -123.97583066087832 41.31852640120816, -124.25710598001243 41.15352132907401, -124.51409805934621 40.96800014522892, -124.74433194261869 40.763912348675035, -124.94567706168226 40.54338210199239,
-125.11636173536279 40.30868123071627, -125.25498087780294 40.06220148128715, -125.3604974831004 39.80642653665781, -125.4322385960062 39.543904229883005, -125.46988656305209 39.277219329961135, -125.4734663894492
39.008967205820475, -125.44333001234564 38.74172860785035, -125.38013825025583 38.47804574501649, -125.28484111194828 38.22039978159673, -125.1586570556347 37.971189832187214, -125.00305168962673 37.73271349727281,
-124.8197163058454 37.50714895406215, -124.61054654308778 37.296538597688055, -124.37762139148631 37.102774215181654, -124.12318267532315 36.9275836675835, -123.8496150891857 36.772519052867715, -123.55942681226277
36.638946322795874, -123.25523068653888 36.52803632929597, -122.93972591543192 36.44075727956827, -122.61568021845359 36.377868583149755, -122.28591236310895 36.339916078129036, -121.9532749859139 36.327228627297,
-121.62063760871888 36.339916078129036, -121.2908697533742 36.377868583149755, -120.96682405639588 36.44075727956827, -120.65131928528895 36.52803632929597, -120.34712315956506 36.638946322795874, -120.0569348826421
36.772519052867715, -119.78336729650465 36.9275836675835, -119.52892858034149 37.102774215181654, -119.29600342874002 37.29653859768806, -119.08683366598238 37.50714895406215, -118.90349828220107 37.73271349727281,
-118.7478929161931 37.971189832187214, -118.62170885987955 38.22039978159673, -118.52641172157198 38.47804574501649, -118.46321995948216 38.74172860785035, -118.43308358237861 39.008967205820475, -118.43666340877571
39.277219329961135, -118.4743113758216 39.543904229883005, -118.54605248872741 39.80642653665781, -118.65156909402486 40.06220148128715, -118.79018823646503 40.30868123071627, -118.96087291014557 40.54338210199239,
-119.16221802920913 40.763912348675035, -119.3924519124816 40.96800014522892, -119.6494439918154 41.15352132907401, -119.93071931094948 41.31852640120816, -120.23348018018605 41.461266240272025, -120.55463509747037 41.58021595697532, -120.89083474998958 41.67409631073075, -121.2385145894895 41.74189213171878, -121.59394315124284 41.7828672412252, -122.31260682058497 41.7828672412252)), ((-119.1795222467484 42.50521242789702, -120.70099431758788 39.07636493660857, -115.32512633395542 38.91870544294517, -119.1795222467484 42.50521242789702)))'
INSERT INTO #customPolygon
SELECT geography::STPolyFromText(#customPolygon, 4326).MakeValid().ToString()
UPDATE #customPolygon SET geog=case when geog.EnvelopeAngle() > 90 then geog.ReorientObject() else geog end
SET #customPolygonJoin = ' join #customPolygon poly on poly.geog.STIntersects(a.GeoLoc) = 1 '][1]][1]
I would like to avoid itemizing polygons within the multipolygon string as there could be an unlimited number.
I've tried ST unions and ST difference, except it seems those require two geography inputs, where the multipolgyon is just 1.
TYIA
I think this "hole" is artifact of your drawing tool. Within SQL Server, it is two overlapping polygons - so there is no hole, it is instead covered by both of the polygons.
But if you want to dissolve this into a single polygon, I would try to StUnion it with empty geography (geography::STGeomFromText('POLYGON EMPTY', 4326)) or with itself.
I have downloaded a shapefile from Ordinance Survey website, and imported it into SQL using ShpToSql.exe, here the setup
This imports fine.
Now i want to query what region a particular longitude and latitude is within.
Using the following
Postcode: WD25 7LR (Harry Potter Studios :D)
Latitude: 51.6910751568794
Longitude: -0.418128358906299
I thought i could write something like
DECLARE #g geography
set #g = geography::Point(51.6910751568794, -0.418128358906299, 4326)
select [name] from region where #g.STWithin(geom) is not null
But that returns an error message of Operand type clash: geometry is incompatible with geography
So i tried to change the data type to geometry, so code looks like this
declare #g geometry
set #g = geometry::Point(51.6910751568794, -0.418128358906299, 4326)
select [name] from region where #g.STWithin(geom) = 1
But no results are returned.
Can someone help me with this please. Just want to know if a longitude and latitude is within a particular POLYGON.
UPDATE:
I have tried to import the .shp file using Geography data type, but this gives an error message when i try to import it
And even if i still try to import it, i them get a message like this for every shape in the shp file
SQL Server will not allow comparisons between geometry and geography data types.
If you are not concerned with being exact, you could perform your original query with the point as a geometry type. This will work reasonably well in most small cases where you aren't comparing odd shapes and across hemispheres.
DECLARE #g geometry
set #g = geometry::Point(51.6910751568794, -0.418128358906299, 4326)
select [name] from region where #g.STWithin(geom) is not null
Otherwise you will need to import the data as a geography type and based on your note there might be some malformed data in the shapefile.
Does anybody know what is the problem with my query. I am trying to calculate area using geographical coordinates, but result seems to be too small to be true. 0.00118 sqm. Can anybody help?
SELECT ST_Area(the_geom) As sqm
FROM (SELECT
ST_GeomFromText('POLYGON
(
(14.604514925547997 121.0968017578125,
14.595212295624522 121.08512878417969,
14.567302046916149 121.124267578125,
14.596541266841905 121.14761352539062,
14.604514925547997 121.0968017578125)
)',4326) ) As foo(the_geom)
How accurate should be the calculation?
A solution is to cast GEOMETRY to GEOGRAPHY, which is acceptably accurate for the most use cases:
SELECT ST_Area(the_geom::GEOGRAPHY ) As sqm
FROM (SELECT
ST_GeomFromText('POLYGON
(
(14.604514925547997 121.0968017578125,
14.595212295624522 121.08512878417969,
14.567302046916149 121.124267578125,
14.596541266841905 121.14761352539062,
14.604514925547997 121.0968017578125)
)',4326) ) As foo(the_geom)
The geography type automatically converts degrees to meters.
Depending on your scenario you could also use directly the geography constructor St_GeographyFromText, which accept a WKT string as argument, very similar to ST_GeomFromText
ST_GeographyFromText('POLYGON((14.604514925547997 121.0968017578125,
14.595212295624522 121.08512878417969,
14.567302046916149 121.124267578125,
14.596541266841905 121.14761352539062,
14.604514925547997 121.0968017578125))'
)
I have a collection of lat/long pairs that specify the coordinates of property. An example of such would be this:
(-97.7157864909875 30.406523562241, -97.7165355983733 30.4068866164923, -97.716787930159 30.4064954568619, -97.7168253595963 30.4065335493939, -97.7168568837126 30.4065754656014, -97.7168819885038 30.4066205220471, -97.716901410079 30.4066619534041, -97.7169158736828 30.4066896672646, -97.7169327718411 30.4067163205123, -97.716952004751 30.4067417571518, -97.7169734604111 30.4067658281043, -97.7176225812739 30.4057595267431, -97.7168902352123 30.4054046115321, -97.7164489526149 30.4060840883432, -97.7163106372336 30.4061380633337, -97.7158545237879 30.4059170368804, -97.7158294889129 30.4060371739058, -97.7158101406138 30.4061580975546, -97.7157965112558 30.4062796056817, -97.7157886236446 30.4064014951642, -97.7157864909875 30.406523562241)
Lets say I have maybe 30K or so of these in a table.
Then I have a single lat/lon pair and I need to know which of the polygons (could be more than one) does this point fall inside of.
I have very limited experience with spatial types and I am trying ensure I can properly define indexes on this to gain the speed I need with this query.
Any help you can offer to get me headed in the right direction is greatly appreciated.
I believe I can do it like this:
DECLARE #CurrentPosition geography
declare #Line geography
DECLARE #result geography
SET #CurrentPosition = geography::STGeomFromText('POINT(lat lon)', 4326)
set #Line = geography::STGeomFromText('LINESTRING(point collection)', 4326)
SELECT #result = #Line.STIntersection(#CurrentPosition)
select #result.ToString()
This will help with the actual is it inside the line or not - but the question I am struggling with is how to define the selection statement to perform the above transaction when I am searching the table for the items that intersect.
Thanks
Environment: SQL Server 2012
I'm using an online tool, the only one I could find so far, to plot polygons and points on the earth. http://www.birdtheme.org/useful/googletool.html
I have two tables. One stores "areas" as polygons and the other table stores points amongst other things irrelevant to my question.
For simplicity, I'll just reduce my scenario to sql variables.
In the query below, I'm using the geography data type for well known points of interest.
I drew a polygon around Robben Island, a point in Robben Island and a point in Alcatraz.
DECLARE #robben_island geography = ('POLYGON((18.351803 -33.788421,18.382788 -33.787494,18.386736 -33.820515,18.354464 -33.822369,18.351803 -33.788421))')
DECLARE #point_in_robben_island geography= ('POINT(18.369226 -33.80554)')
DECLARE #point_in_alcatraz geography= ('POINT(-122.423401 37.827006)')
SELECT #robben_island.STContains(#point_in_robben_island) --returns 'False', but it's not what I expected
SELECT #robben_island.STContains(#point_in_alcatraz) --returns 'True', but it's not what I expected
This query above, if I understand it correctly, tells me that my #point_in_robben_island is not contained in #robben_island, rather my #point_in_alcatraz exists in #robben_island which as we all know, is not true.
Now when I change the data types from geography to geometry, everything works fine, but I'm afraid that if I continue using the geometry data type I might come across a few gotchas. I'm just wondering if I won't be negatively affected by fact that geometry doesn't quite account for earth's curvature. touch wood.
DECLARE #robben_island geometry = ('POLYGON((18.351803 -33.788421,18.382788 -33.787494,18.386736 -33.820515,18.354464 -33.822369,18.351803 -33.788421))')
DECLARE #point_in_robben_island geometry= ('POINT(18.369226 -33.80554)')
DECLARE #point_in_alcatraz geometry= ('POINT(-122.423401 37.827006)')
SELECT #robben_island.STContains(#point_in_robben_island) --returns 'True' as it should
SELECT #robben_island.STContains(#point_in_alcatraz) --returns 'False' as it should
Now my question is, why does the geography data type return unexpected results while geometry works as expected? Thank you very much.
The geography type is a little bit more restrictive than geometry. It can't cross different hemispheres and the outer ring must be drawn counter-clockwise.
Unfortunately (some find this a good thing), SQL Server 2012 no longer throws an error when you create the invalid geography. You need to invert the order of the points in the Roben Island geometry, like:
DECLARE #robben_island geography = ('POLYGON((18.351803 -33.788421, 18.354464 -33.822369,18.386736 -33.820515, 18.382788 -33.787494, 18.351803 -33.788421))')
DECLARE #point_in_robben_island geography= ('POINT(18.369226 -33.80554)')
DECLARE #point_in_alcatraz geography= ('POINT(-122.423401 37.827006)')
SELECT #robben_island.STContains(#point_in_robben_island) --returns 'True'
SELECT #robben_island.STContains(#point_in_alcatraz) --returns 'False'