Herman, I can't begin to tell you how much I appreciate you doing this! Thanks so much!!
I'm off my computer for the day, but will run it through its paces tomorrow. Thanks again! Bill P William Prothero http://es.earthednet.org > On Jun 30, 2017, at 8:27 PM, hh via use-livecode > <use-livecode@lists.runrev.com> wrote: > > Sorry all, I'm used to work in the forums where one can easily edit posts to > remove errors and typos. > > So here another correction, a constant (pixelsPerLonRadian) was wrong in the > first two versions above. > > My last version, hope it's all correct now: > > local MERCATOR_RANGE=256, pixelOrigin, pixelsPerLonDegree, pixelsPerLonRadian > > on mouseUp > put (55.9537534, -3.1988236) into centerPoint -- LC Home > put trunc(the thumbpos of sb "zoom") into zom -- zoom > put 600 into wdth -- image width > put 450 into hght -- image height > put getCorners (centerpoint,zom,wdth,hght) > -- result is "SW: 55.780374,-3.610811,NE: 56.126359,-2.786836" > end mouseUp > > function getCorners center,zom,mapWidth,mapHeight > put (MERCATOR_RANGE/2, MERCATOR_RANGE/2) into pixelOrigin > put MERCATOR_RANGE/360 into pixelsPerLonDegree > put MERCATOR_RANGE/2/pi into pixelsPerLonRadian > put 2^zom into scle > put fromLatLngToPoint(center) into centerPx > put ( (item 1 of centerPx)-(mapWidth/2)/scle, \ > (item 2 of centerPx)+(mapHeight/2)/scle ) into SWPoint > put fromPointToLatLng(SWPoint) into SWLatLon > put ( (item 1 of centerPx)+(mapWidth/2)/scle, \ > (item 2 of centerPx)-(mapHeight/2)/scle ) into NEPoint > put fromPointToLatLng(NEPoint) into NELatLon > return ("SW: " & SWLatLon, "NE: "& NELatLon) > end getCorners > > function bound val, opt_min, opt_max > if (opt_min is not empty) then put max(val, opt_min) into val > if (opt_max is not empty) then put min(val, opt_max) into val > return val > end bound > > function degreesToRadians deg > return deg * pi / 180; > end degreesToRadians > > function radiansToDegrees rad > return 180 * rad / pi > end radiansToDegrees > > function fromLatLngToPoint latLng, opt_point > put opt_point into point > put pixelOrigin into origin > put (item 1 of origin)+(item 2 of latLng)*pixelsPerLonDegree into item 1 of > point > put bound(sin(degreesToRadians(item 1 of latLng)), -0.9999, 0.9999) into siny > put (item 2 of origin)+0.5*ln((1-siny)/(1+siny))*pixelsPerLonRadian into > item 2 of point > return point > end fromLatLngToPoint > > function fromPointToLatLng point > put pixelOrigin into origin > put (item 1 of point -item 1 of origin)/pixelsPerLonDegree into lng > put (item 2 of origin-item 2 of point)/pixelsPerLonRadian into latRadians > put radiansToDegrees(2*atan(exp(latRadians))-pi/2) into lat > return (lat,lng) > end fromPointToLatLng > > // pixelCoordinate = worldCoordinate * 2^zoomLevel > > > _______________________________________________ > use-livecode mailing list > use-livecode@lists.runrev.com > Please visit this url to subscribe, unsubscribe and manage your subscription > preferences: > http://lists.runrev.com/mailman/listinfo/use-livecode _______________________________________________ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
