A map marker usually lands in the wrong place because the coordinates were interpreted differently from how they were produced. Check, in order: coordinate order, coordinate reference system and units, signs and ranges, conversions between geographic and display coordinates, and—if the point came from an address—the geocoder’s returned match.
Start with one raw record and label what each value means
Before changing the marker code, log one source record exactly as received. Label its fields explicitly: latitude, longitude, x, y, CRS or datum, and units. A pair such as 40.7, -74.0 is not self-describing; its meaning depends on the format and the coordinate system that produced it.
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Then follow that record through each boundary: source file, parser, transformation, map API, and rendering code. A value can be valid at one stage and wrong for the next if its order, CRS, units, or coordinate space changes.
1. Latitude and longitude may be reversed
Coordinate order depends on the receiving format or API, not on a universal rule. Google Maps JavaScript LatLng takes latitude first and longitude second. RFC 7946 GeoJSON uses longitude first, then latitude—the x/y order. The Google Maps reference explains that although longitude is the map’s x-coordinate, latitude is written first in LatLng (Google Maps JavaScript coordinates reference). The GeoJSON standard specifies the position order (RFC 7946).
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For example, a location near New York might appear in GeoJSON as [-74.0, 40.7], but the corresponding Google Maps JavaScript constructor is new google.maps.LatLng(40.7, -74.0). Reversing those values can put the point somewhere entirely different—or produce invalid latitude.
PROJ also documents why an authority-defined CRS axis order can differ from the order a person expects in a particular command-line interface. Check the specific CRS and tool instead of relying on a remembered convention (PROJ FAQ on axis ordering).
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2. The numbers may use the wrong CRS, projection, or units
Correct order does not make coordinates usable if they are expressed in the wrong reference system. RFC 7946 GeoJSON uses WGS 84 geographic coordinates in decimal degrees. By contrast, projected data may use easting and northing in metres or another linear unit. Passing projected x/y values to an interface expecting longitude and latitude can place features far from their intended locations.
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3. A sign, range, or parsing mistake can survive into the map
For geographic decimal degrees, west longitudes and south latitudes are negative. A dropped minus sign can move a point to the opposite side of the equator or prime meridian. Also check decimal separators, field mapping, string-to-number parsing, and whether a value was accidentally read in the wrong column.
Google Maps JavaScript LatLng expects latitude from -90 to 90 and longitude from -180 to 180. Its handling may clamp latitude or wrap longitude, which can make an invalid upstream value look like a plausible marker rather than a clear error (Google Maps JavaScript coordinates reference). Validate and reject or flag out-of-range values before calling the map API instead of depending on renderer behavior.
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4. Geographic coordinates are not pixels, tiles, or projected metres
Mapping code often moves a point through several coordinate spaces. Google Maps JavaScript converts latitude and longitude into Mercator world coordinates, then uses pixel and tile coordinates for display. These values are not interchangeable: a screen pixel, tile index, projected metre coordinate, or marker-icon anchor must not be passed where geographic latitude and longitude are expected.
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Trace each conversion and annotate its input and output units. Confirm that the marker position and map view refer to the same coordinate space, and check whether a screen offset or icon anchor is being applied as though it were part of the geographic location. Google’s documentation notes that the Mercator map has an image cutoff near approximately 85 degrees north and south, so ordinary Mercator tiles do not display latitude as an unbounded scale toward the poles (Google Maps coordinate systems).
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5. The marker may be showing an unexpected geocoder match
If a point came from an address, the marker may be faithfully plotting a candidate that is not the place you intended. Inspect the complete geocoding response—not just the coordinates—including the formatted address, place ID, geometry, and result type. Google recommends its Geocoding API for complete, unambiguous addresses; for real-time incomplete or ambiguous input, its guidance recommends Places Autocomplete to obtain a place ID and then geocode that ID (Google geocoding best practices).
Geocoding accuracy varies by country. Google’s Maps Platform FAQ recommends checking location_type to judge whether a result is appropriate for the use case (Google Maps Platform FAQ: geocoding accuracy). A plausible coordinate alone does not establish that the returned address is the right one.
Debug the marker in a reliable order
- Log a source record. Record the raw values and label latitude, longitude, x, y, CRS, and units rather than relying on column positions.
- Check order at every boundary. Inspect the first two values in GeoJSON positions; check latitude and longitude separately for Google Maps
LatLng. - Validate signs and ranges. Confirm west and south signs, numeric parsing, and expected bounds before making the map call. Flag out-of-range values explicitly.
- Confirm CRS and units. Compare the source reference system with the receiving service’s requirements and reproject explicitly when they differ.
- Trace display conversions. Label geographic, projected, world, pixel, and tile values, and check that offsets or icon anchors are not being mixed into a geographic position.
- Inspect geocoder output. Verify the returned address, place ID, geometry, and result quality; choose an input flow suited to complete versus ambiguous address text.
- Compare a known point. Plot a known test location and compare it with a second independent coordinate display. A visual match can catch order or gross placement mistakes, but it does not prove datum or source accuracy.
More decimal places do not guarantee a more accurate marker
The authors of RFC 7946 state that six decimal places in geographic coordinates amount to about 10 centimetres, while noting that expanding many detailed GeoJSON coordinates from six to 15 decimal places can nearly double text size (RFC 7946, 2016). Those figures describe coordinate representation, not a guarantee that the source location is accurate to that distance. Source quality, transformations, and display resolution also matter.
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Google’s Maps Static API ignores location-parameter precision beyond six decimal places, according to its current documentation accessed in 2026 (Maps Static API documentation). That is specific to those parameters; it should not be generalized to every mapping interface. In neither case will extra digits repair a swapped order, wrong CRS, parsing error, or poor geocoder match.
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