This article explains the fundamentals of geographic and projected coordinate systems, details the Mercator and Web Mercator projections, introduces EPSG standards, discusses China's GCJ02 and BD09 offsets, and describes common GIS data services and tile‑based rendering techniques.
The article explains why flat maps require projections, compares conformal, equal‑area and equidistant methods, describes the WGS84 datum and the GCJ‑02 “Mars” offset, outlines modern Web Mercator tiling standards, and shows how Python libraries like mercantile, pygrib, xarray, GDAL and rasterio can be used to read gridded data and produce map tiles.
The article explains high‑precision mapping fundamentals, from Earth’s ellipsoid and geoid definitions and common datums to 2‑D map projections, then details vehicle‑centred and sensor coordinate frames (ECEF, ENU, body, LiDAR, IMU, camera), their transformations, rotation representations, and key standards such as EPSG and Proj.4.
This article details the design and implementation of an ARKit‑based hotel‑finding application for iOS, covering coordinate system concepts, conversion pipelines, elevation handling, directional hints, radar visualization, navigation routing, map/AR switching, and real‑time navigation alerts, accompanied by sample Objective‑C code.
The article examines typical coordinate‑system and accuracy problems encountered when implementing location and map features on iOS and Android, explains why they occur, and shares Ctrip's practical solutions including coordinate conversion, Wi‑Fi handling, and WebView‑based map rendering.
