epsg-mcp

{ "version": "1.0.0", "topics": { "japan_survey": { "description": "Best practices for CRS selection in surveying and mapping within Japan", "practices": [ { "title": "Use JGD2011 (EPSG:6668) as the standard", "description": "Use JGD2011 based on the Survey Act for surveying and mapping within Japan", "priority": "must", "rationale": "Official geodetic datum of Japan with consistency with GSI products", "example": "Creating base maps, cadastral maps, urban planning maps" }, { "title": "Select the appropriate Japan Plane Rectangular CS", "description": "Select the appropriate Japan Plane Rectangular CS (Zone I-XIX) for the target area", "priority": "must", "rationale": "Different zones mean different coordinate values, leading to inaccurate calculations", "example": "Tokyo → Zone IX (EPSG:6677), Sapporo, Hokkaido → Zone XII (EPSG:6680)" }, { "title": "Manage wide-area data in geographic CRS", "description": "Store data spanning multiple zones in geographic CRS (EPSG:6668) and project as needed", "priority": "should", "rationale": "Prevents loss of continuity at zone boundaries" }, { "title": "Use appropriate decimal places based on coordinate precision", "description": "Plane rectangular coordinates: millimeter precision (3 decimal places), Geographic coordinates: approximately 8 decimal places", "priority": "should", "rationale": "Excessive precision is meaningless, insufficient precision degrades data quality" } ], "commonMistakes": [ { "mistake": "Using Tokyo Datum (EPSG:4301)", "consequence": "1-2m coordinate difference from JGD2011 causes misalignment with other data", "solution": "Convert to JGD2011 and record conversion history in metadata" }, { "mistake": "Treating data from different zones as the same zone", "consequence": "Coordinate values differ greatly, causing inaccurate calculations", "solution": "Verify zone information of data and transform coordinates as needed" } ], "relatedTopics": ["precision_requirements", "projection_selection", "historical_data"], "references": [ { "title": "GSI - About JGD2011", "url": "https://www.gsi.go.jp/sokuchikijun/jgd2011.html", "type": "official" }, { "title": "Standards for Public Survey Work Procedures", "url": "https://psgsv2.gsi.go.jp/koukyou/jyunsoku/", "type": "official" } ] }, "web_mapping": { "description": "Best practices for CRS selection in web application map display and interaction", "practices": [ { "title": "Use Web Mercator (EPSG:3857) for web map display", "description": "Standard tile coordinate system for Leaflet, MapLibre, Google Maps, etc.", "priority": "must", "rationale": "Major web map libraries and tile services adopt this coordinate system", "example": "Map tile URL: https://tile.openstreetmap.org/{z}/{x}/{y}.png" }, { "title": "Output GeoJSON in WGS84 (EPSG:4326)", "description": "WGS84 is the standard in the GeoJSON specification", "priority": "must", "rationale": "Ensures interoperability through specification compliance", "codeExample": "{ \"type\": \"Point\", \"coordinates\": [139.6917, 35.6895] }" }, { "title": "Do not perform area/distance calculations in Web Mercator", "description": "When accurate area/distance calculations are needed, convert to geographic CRS or appropriate projected CRS", "priority": "must", "rationale": "Web Mercator has significant area distortion at high latitudes (4x at 60° latitude)" }, { "title": "Use appropriate projected CRS for high-precision functions", "description": "Convert to purpose-appropriate coordinate system for distance measurement, area calculation, buffer generation, etc.", "priority": "should", "rationale": "Minimize errors from projection distortion" } ], "commonMistakes": [ { "mistake": "Calculating area in Web Mercator", "consequence": "Approximately 23% area distortion even in Japan (around 35° latitude)", "solution": "Convert to JGD2011 Plane Rectangular CS or equal-area projection before area calculation" }, { "mistake": "Outputting EPSG:3857 coordinates in GeoJSON", "consequence": "Cannot be read correctly by other GIS software", "solution": "Output GeoJSON in WGS84 (EPSG:4326), omit CRS property" } ], "relatedTopics": ["data_exchange", "coordinate_storage"], "references": [ { "title": "GeoJSON Specification (RFC 7946)", "url": "https://datatracker.ietf.org/doc/html/rfc7946", "type": "official" }, { "title": "Leaflet Documentation", "url": "https://leafletjs.com/reference.html", "type": "tool" } ] }, "data_exchange": { "description": "Best practices for CRS selection in data exchange between organizations and systems", "practices": [ { "title": "Include CRS information in data", "description": "Include EPSG code in metadata and record transformation history", "priority": "must", "rationale": "Data with unknown CRS causes confusion during use", "example": "Shapefile .prj file, GeoPackage spatial_ref_sys table" }, { "title": "Use WGS84 for international data exchange", "description": "Use WGS84 (EPSG:4326) as the reference for data exchange across countries and regions", "priority": "should", "rationale": "Reference for GPS satellites and universally recognized worldwide" }, { "title": "Specify transformation accuracy", "description": "When coordinate transformation is performed, record transformation method and accuracy in metadata", "priority": "should", "rationale": "Allows recipients to evaluate accuracy" } ], "commonMistakes": [ { "mistake": "Providing data without CRS information", "consequence": "Recipients interpret incorrect coordinate system, causing position misalignment", "solution": "Always include CRS information (EPSG code) in metadata" } ], "relatedTopics": ["coordinate_storage", "cross_border"], "references": [ { "title": "ISO 19115 - Geographic information — Metadata", "type": "official" } ] }, "coordinate_storage": { "description": "Best practices for storing coordinate data in databases and files", "practices": [ { "title": "Use geographic CRS for long-term storage", "description": "Store in geographic CRS (EPSG:4326 or EPSG:6668) in databases", "priority": "should", "rationale": "Projected CRS may change in the future, but geographic CRS is stable" }, { "title": "Use numeric types appropriate for coordinate precision", "description": "DOUBLE type for lat/lon, DECIMAL(12,3) or similar for projected coordinates", "priority": "should", "rationale": "FLOAT type may have insufficient precision" }, { "title": "Unify CRS for spatial indexes", "description": "Use a unified CRS when creating spatial indexes in PostGIS, etc.", "priority": "must", "rationale": "Data in different CRS cannot be correctly compared in spatial queries" } ], "commonMistakes": [ { "mistake": "Storing coordinates in FLOAT type", "consequence": "Only about 7 digits of precision, potentially 10m or more error in lat/lon", "solution": "Use DOUBLE type or DECIMAL type" } ], "relatedTopics": ["precision_requirements", "gis_integration"], "references": [ { "title": "PostGIS Documentation", "url": "https://postgis.net/documentation/", "type": "tool" } ] }, "mobile_gps": { "description": "Best practices for using location information on smartphones and GPS devices", "practices": [ { "title": "Recognize that GPS output is WGS84", "description": "GPS satellite systems use WGS84, and output coordinates are also WGS84", "priority": "must", "rationale": "Misidentifying the datum causes 1-2m or more displacement" }, { "title": "Understand GPS accuracy limitations", "description": "Consumer GPS: several meters to 10m, DGPS: about 1m, RTK: several cm", "priority": "should", "rationale": "Discussions beyond accuracy are meaningless" }, { "title": "Convert to JGD2011 for storing data within Japan", "description": "WGS84 and JGD2011 are practically identical, but conversion recommended for consistency in domestic data management", "priority": "may", "rationale": "Coordinate difference is within a few cm, but maintains metadata consistency" } ], "commonMistakes": [ { "mistake": "Treating GPS data as Tokyo Datum", "consequence": "Displacement of 400m or more from actual position", "solution": "Recognize that GPS output is WGS84 and process appropriately" } ], "relatedTopics": ["precision_requirements", "japan_survey"], "references": [ { "title": "How GPS Works - GSI Japan", "url": "https://www.gsi.go.jp/denshi/denshi_g-01.html", "type": "official" } ] }, "historical_data": { "description": "Best practices for handling data created in the past", "practices": [ { "title": "Convert Tokyo Datum data before use", "description": "Convert Tokyo Datum (EPSG:4301) data to JGD2011 before use", "priority": "must", "rationale": "Ensures consistency with current geodetic datum", "example": "Two-step conversion: EPSG:4301 → EPSG:4612 → EPSG:6668" }, { "title": "Recognize transformation accuracy limitations", "description": "Tokyo Datum → JGD2011 transformation accuracy is limited to 1-2m", "priority": "must", "rationale": "Discussions beyond accuracy are meaningless; compare with precision requirements" }, { "title": "Preserve original datum information", "description": "Retain original datum information and parameters as metadata even after conversion", "priority": "should", "rationale": "Needed for future verification or re-transformation" } ], "commonMistakes": [ { "mistake": "Using old data without datum information as-is", "consequence": "Large displacement when overlaying with new data", "solution": "Investigate data origin, estimate appropriate datum, and transform" } ], "relatedTopics": ["japan_survey", "precision_requirements"], "references": [ { "title": "JGD2000/2011 - GSI Japan", "url": "https://www.gsi.go.jp/sokuchikijun/sokuchikijun_top.html", "type": "official" } ] }, "cross_border": { "description": "Best practices for CRS selection in cross-border data and international projects", "practices": [ { "title": "Use WGS84 as the common reference", "description": "Use WGS84 (EPSG:4326) as the reference coordinate system for international data exchange", "priority": "must", "rationale": "Universally recognized worldwide and reference for GPS satellites" }, { "title": "Utilize UTM coordinate system", "description": "Use UTM zones when wide-area projected coordinates are needed", "priority": "should", "rationale": "Defined worldwide with high interoperability", "example": "Japan: UTM 52N-54N (EPSG:32652-32654)" } ], "commonMistakes": [ { "mistake": "Merging national geodetic datums directly", "consequence": "Data discontinuity occurs near borders", "solution": "Convert to common coordinate system (WGS84, etc.) before merging" } ], "relatedTopics": ["data_exchange", "projection_selection"], "references": [ { "title": "EPSG Registry", "url": "https://epsg.org/", "type": "official" } ] }, "gis_integration": { "description": "Best practices for handling CRS in GIS software and system integration", "practices": [ { "title": "Clearly define project CRS", "description": "Determine CRS at project start and document it", "priority": "must", "rationale": "Later changes cause significant rework" }, { "title": "Don't over-rely on on-the-fly transformation", "description": "On-the-fly transformation for display is convenient, but explicitly transform before analysis/output", "priority": "should", "rationale": "On-the-fly transformation affects performance and can cause unexpected rounding errors" }, { "title": "Verify CRS when loading data", "description": "Check CRS information before loading new data", "priority": "should", "rationale": "Prevents mixing of data with unknown or incorrect CRS" } ], "commonMistakes": [ { "mistake": "Setting CRS for unknown data based on guesswork", "consequence": "All spatial calculation results become inaccurate if actual CRS differs", "solution": "Verify data source, contact provider if necessary" } ], "relatedTopics": ["coordinate_storage", "data_exchange"], "references": [ { "title": "QGIS Documentation", "url": "https://qgis.org/documentation/", "type": "tool" } ] }, "precision_requirements": { "description": "Setting and achieving precision requirements according to use case", "practices": [ { "title": "Set precision according to use case", "description": "Car navigation: several meters, Urban planning: tens of cm, Surveying: sub-cm", "priority": "must", "rationale": "Excessive precision increases cost, insufficient precision fails requirements" }, { "title": "Select coordinate system appropriate for precision", "description": "Projected CRS for high precision needs, Geographic CRS for wide areas", "priority": "should", "rationale": "Match coordinate system characteristics with precision requirements" } ], "commonMistakes": [ { "mistake": "Expecting millimeter precision from GPS data", "consequence": "Discussion beyond measurement limits becomes meaningless precision debate", "solution": "Understand the precision limits of data sources" } ], "relatedTopics": ["mobile_gps", "japan_survey"], "references": [ { "title": "Survey Accuracy Classes - MLIT Japan", "type": "official" } ] }, "projection_selection": { "description": "How to select projection methods according to purpose", "practices": [ { "title": "Select projection method according to purpose", "description": "Conformal projection (shape preservation), Equal-area projection (area preservation), Equidistant projection (distance preservation)", "priority": "must", "rationale": "Impossible to preserve all characteristics simultaneously" }, { "title": "Use Japan Plane Rectangular CS for surveying in Japan", "description": "Transverse Mercator (conformal) enables high-precision distance and angle calculations", "priority": "should", "rationale": "Standard for public surveys and legally recognized" }, { "title": "Use Web Mercator for web maps", "description": "Can represent the entire world on a single map and compatible with tile division", "priority": "should", "rationale": "De facto standard for web maps" } ], "commonMistakes": [ { "mistake": "Creating statistical maps with Web Mercator", "consequence": "High-latitude areas are exaggerated in area, causing misunderstanding", "solution": "Use equal-area projection for statistical maps" } ], "relatedTopics": ["web_mapping", "japan_survey"], "references": [ { "title": "Map Projections - GSI Japan", "url": "https://www.gsi.go.jp/KIDS/map-sign-tizutohou-tizutohou.html", "type": "official" } ] } } }