epsg-mcp

{ "version": "1.0.0", "symptoms": { "coordinate_shift_large": { "description": "Coordinates shifted by hundreds of meters to kilometers", "keywords": [ "hundreds of meters", "kilometers", "completely wrong", "large shift", "400m", "several hundred meters" ], "possibleCauses": [ { "likelihood": "high", "cause": "Datum mix-up (Tokyo Datum vs JGD/WGS84)", "description": "There is a systematic shift of approximately 400m between Tokyo Datum and JGD2011/WGS84", "indicators": [ "Data created before 2002", "Digitized from old maps or drawings", "CRS information is unknown or not set" ] }, { "likelihood": "medium", "cause": "Incorrect CRS assignment", "description": "Data's CRS information is set to a different value than the actual CRS", "indicators": [ "CRS was manually specified during import", ".prj file is missing or incorrect", "Post-transformation CRS is set without actual transformation" ] }, { "likelihood": "low", "cause": "Axis swap (X/Y, longitude/latitude)", "description": "Longitude and latitude are swapped, or X/Y order is reversed", "indicators": [ "Points appear in the ocean or foreign countries", "Coordinate value ranges differ from expectations" ] } ], "diagnosticSteps": [ { "step": 1, "action": "Check the data's CRS information", "expected": "A clear EPSG code is set", "ifFailed": "If CRS is unknown, investigate data origin" }, { "step": 2, "action": "Check coordinate value ranges", "expected": "For Japan: latitude 20-46°, longitude 122-154°", "ifFailed": "If values are abnormal, suspect axis swap" }, { "step": 3, "action": "Compare coordinates of known points", "expected": "Matches reference data", "ifFailed": "Estimate cause from shift pattern (direction, distance)" } ], "solutions": [ { "forCause": "Datum mix-up (Tokyo Datum vs JGD/WGS84)", "steps": [ "Confirm data is in Tokyo Datum", "Perform transformation from EPSG:4301 to EPSG:6668", "Verify transformed data" ], "prevention": "Document datum when creating data, transform old data before use", "tools": ["QGIS", "GDAL ogr2ogr", "PostGIS ST_Transform"] }, { "forCause": "Incorrect CRS assignment", "steps": [ "Identify the correct CRS", "Correct CRS information (change definition, not transform)", "Verify corrected data" ], "prevention": "Always verify CRS information when obtaining data and document it" } ], "relatedBestPractices": ["historical_data", "data_exchange"] }, "coordinate_shift_medium": { "description": "Coordinates shifted by 1 to several meters", "keywords": [ "several m", "1-2m", "meter scale", "1m", "2m", "a few meters", "off by", "meters", "1-2 meters", "couple meters" ], "possibleCauses": [ { "likelihood": "high", "cause": "Tokyo Datum to JGD2011 transformation accuracy", "description": "Tokyo Datum → JGD2011 transformation accuracy is limited to 1-2m", "indicators": ["Transformation from Tokyo Datum was performed", "Using old data"] }, { "likelihood": "medium", "cause": "Different transformation parameters", "description": "Same transformation can produce different results depending on parameters used", "indicators": ["Results differ between software", "Transformation method not documented"] } ], "diagnosticSteps": [ { "step": 1, "action": "Check transformation history", "expected": "Transformation method and parameters are recorded", "ifFailed": "If transformation is unclear, verify original data" }, { "step": 2, "action": "Verify transformation accuracy limits", "expected": "1-2m shift is normal for Tokyo→JGD transformation", "ifFailed": "If shift is larger, investigate other causes" } ], "solutions": [ { "forCause": "Tokyo Datum to JGD2011 transformation accuracy", "steps": [ "Accept 1-2m shift as transformation accuracy limit", "Consider re-surveying original data if higher accuracy needed", "Record transformation accuracy in metadata" ], "prevention": "Verify data precision requirements and transformation accuracy limits beforehand" } ], "relatedBestPractices": ["historical_data", "precision_requirements"] }, "coordinate_shift_small": { "description": "Coordinates shifted by centimeters to tens of centimeters", "keywords": ["few cm", "centimeters", "minor", "cm", "tens of cm"], "possibleCauses": [ { "likelihood": "high", "cause": "Difference between WGS84 and JGD2011", "description": "WGS84 and JGD2011 are practically identical but strictly differ by a few cm", "indicators": [ "Mixed use of GPS(WGS84) and JGD2011 data", "Using high-precision survey data" ] }, { "likelihood": "medium", "cause": "Crustal deformation correction from JGD2000 to JGD2011", "description": "Coordinates changed due to crustal deformation from the 2011 Tohoku earthquake", "indicators": ["Using JGD2000 data from before 2011", "Data from Tohoku region"] }, { "likelihood": "low", "cause": "Numerical precision/rounding errors", "description": "Insufficient decimal places in coordinates or rounding errors during calculations", "indicators": ["Coordinates stored in FLOAT type", "Multiple transformations performed"] } ], "diagnosticSteps": [ { "step": 1, "action": "Check the CRS being used", "expected": "Verify WGS84 and JGD2011 are not mixed", "ifFailed": "Consider unifying if mixed" }, { "step": 2, "action": "Check numeric type", "expected": "DOUBLE type or DECIMAL type with sufficient precision", "ifFailed": "Consider type change if FLOAT type" } ], "solutions": [ { "forCause": "Difference between WGS84 and JGD2011", "steps": [ "Use as-is if no practical issues", "Unify to one if strict consistency needed", "JGD2011 recommended for data within Japan" ], "prevention": "Unify CRS at project start" } ], "relatedBestPractices": ["coordinate_storage", "precision_requirements"] }, "area_distance_error": { "description": "Area or distance calculations are incorrect", "keywords": ["area", "distance", "calculation result", "length", "size", "calculation wrong"], "possibleCauses": [ { "likelihood": "high", "cause": "Calculations in Web Mercator (EPSG:3857)", "description": "Web Mercator has significant area/distance distortion at high latitudes", "indicators": ["Using web map library", "Calculating in EPSG:3857", "High-latitude data"] }, { "likelihood": "medium", "cause": "Planar calculations in geographic CRS", "description": "Calculating distance or area directly with latitude/longitude", "indicators": [ "Using degree-unit coordinates directly in calculations", "Distance calculation using Pythagorean theorem" ] } ], "diagnosticSteps": [ { "step": 1, "action": "Check the CRS used for calculations", "expected": "Appropriate projected CRS (Japan Plane Rectangular CS for Japan)", "ifFailed": "Transformation needed if Web Mercator or geographic CRS" }, { "step": 2, "action": "Calculate expected error", "expected": "Web Mercator at 35° latitude: approximately 23% area distortion", "ifFailed": "Check if error matches expectations" } ], "solutions": [ { "forCause": "Calculations in Web Mercator (EPSG:3857)", "steps": [ "Transform to JGD2011 Plane Rectangular CS before calculation", "Or use spherical calculation formulas (Haversine, etc.)", "Consider equal-area projection for area calculations" ], "prevention": "Do not use Web Mercator for area/distance calculations", "tools": ["PostGIS ST_Area(geography)", "Turf.js"] } ], "relatedBestPractices": ["web_mapping", "projection_selection"] }, "display_blank": { "description": "Data not displayed or appears blank", "keywords": ["not displayed", "blank", "invisible", "disappeared", "nothing shows"], "possibleCauses": [ { "likelihood": "high", "cause": "Out of coordinate range due to CRS mismatch", "description": "Attempting to display data with different CRS in the same view", "indicators": ["Only some layers are not displayed", "Blank areas when zooming"] }, { "likelihood": "medium", "cause": "Coordinate value magnitude mismatch", "description": "Mixing meter units and degree units, or unit system errors", "indicators": [ "Coordinate values are extremely large or small", "Mixing projected and geographic CRS" ] } ], "diagnosticSteps": [ { "step": 1, "action": "Check CRS of each layer", "expected": "Same CRS for all layers, or transformable", "ifFailed": "Unify CRS or verify transformation settings" }, { "step": 2, "action": "Check coordinate value ranges", "expected": "Within expected range (Japan lat/lon, etc.)", "ifFailed": "Data verification needed if values are abnormal" } ], "solutions": [ { "forCause": "Out of coordinate range due to CRS mismatch", "steps": [ "Check project CRS", "Check and unify all layer CRS", "Verify on-the-fly transformation is enabled" ], "prevention": "Check CRS before adding data" } ], "relatedBestPractices": ["gis_integration", "data_exchange"] }, "transformation_error": { "description": "Error occurs during coordinate transformation", "keywords": [ "cannot transform", "error", "failed", "transformation failed", "transform error" ], "possibleCauses": [ { "likelihood": "high", "cause": "Transformation parameters not found", "description": "Transformation parameters for specified CRS pair are not registered in software", "indicators": [ "Transformation between minor CRS", "\"Transformation method not found\" error" ] }, { "likelihood": "medium", "cause": "Invalid CRS code", "description": "Non-existent or deprecated EPSG code specified", "indicators": ["\"CRS not found\" error", "CRS code was manually entered"] } ], "diagnosticSteps": [ { "step": 1, "action": "Verify CRS code validity", "expected": "Code exists in EPSG Registry", "ifFailed": "Research correct code" }, { "step": 2, "action": "Try transformation via intermediate CRS", "expected": "Transformation possible via WGS84 (EPSG:4326)", "ifFailed": "Manually set parameters" } ], "solutions": [ { "forCause": "Transformation parameters not found", "steps": [ "Try two-step transformation via WGS84 (EPSG:4326)", "Update PROJ or GDAL version", "Manually set transformation parameters" ], "prevention": "Use major CRS, avoid specialized CRS", "tools": ["PROJ", "GDAL", "epsg.io"] } ], "relatedBestPractices": ["data_exchange", "cross_border"] } }, "keywordMapping": { "shift": ["coordinate_shift_large", "coordinate_shift_medium", "coordinate_shift_small"], "offset": ["coordinate_shift_large", "coordinate_shift_medium", "coordinate_shift_small"], "misalignment": ["coordinate_shift_large", "coordinate_shift_medium", "coordinate_shift_small"], "off by": ["coordinate_shift_large", "coordinate_shift_medium", "coordinate_shift_small"], "off": ["coordinate_shift_large", "coordinate_shift_medium", "coordinate_shift_small"], "400m": ["coordinate_shift_large"], "hundreds": ["coordinate_shift_large"], "kilometers": ["coordinate_shift_large"], "1-2m": ["coordinate_shift_medium"], "1-2 meters": ["coordinate_shift_medium"], "several meters": ["coordinate_shift_medium"], "few meters": ["coordinate_shift_medium"], "meters": ["coordinate_shift_medium"], "couple meters": ["coordinate_shift_medium"], "few cm": ["coordinate_shift_small"], "centimeters": ["coordinate_shift_small"], "minor": ["coordinate_shift_small"], "area": ["area_distance_error"], "distance": ["area_distance_error"], "length": ["area_distance_error"], "calculation": ["area_distance_error"], "not displayed": ["display_blank"], "blank": ["display_blank"], "invisible": ["display_blank"], "disappeared": ["display_blank"], "cannot transform": ["transformation_error"], "error": ["transformation_error"], "failed": ["transformation_error"] } }