# Web Mapping for Farm Management Information Systems: A Review and Australian Orchard Case Study
## 2 Background
### A Primer on Web Mapping  
[PERSON] et al. [32] reviewed trends in web mapping. Briefly, the use of web map services provides an 'easy' path for the introduction of a mapping capability within a given service, which is supported by easily available training resources, e.g., Beeflamb [33]. ESRI reports a trend for clients to deliver data to customers using WebGIS (such as ArcGIS Online, arcgis.com accessed on 30 September 2023) rather than by the supply of datasets or production of PDFs, providing 'live data in the hands of field operators' [34]. This trend is also true for FMIS, e.g., [PERSON] et al. [35] discuss design principles for the integration of Google Maps into FMIS. Example applications include the use of Google Maps to visualize locations of tens of thousands of small gardens [36] and locations of animal 'exploitation farms' [37]. In non-agricultural examples, GE imagery was used in the display of meteorological satellite data [38], bird species distribution [39], and geochemical data [12]. However, web mapping has several limitations that should be understood in the context of use with FMIS. The default coordinate system for geolocation data is geographic (longitude and latitude, generally in WGS84), measured in degrees for a given earth model. This geographic data are projected for visualization, e.g., for the display of data in FMIS as a two-dimensional view of Earth's surface. This process involves a conversion of geographic data to projected coordinates for a given map type and datum. The commonly used Mercator projection involves a cylindrical projection, distorting the pole regions (such that Greenland appears larger than Africa). A variant of the Mercator projection system that is used in web mapping applications has the official identifier of EPSG:3857 and is known as Web Mercator, ESRI Web Mercator, Google Web Mercator, Spherical Mercator, WGS 84 Web Mercator, and WGS 84/Pseudo-Mercator. The Web Mercator achieved prominence when it was adopted by Google Maps in 2005. Its advantage lies in the use of a spherical (a sphere with a radius of 6,378,137.0 m is assumed) over an ellipsoidal model for the Earth, which requires simpler calculations for the projection of points and thus lower computing resources. However, Web Mercator is not a recognized geodetic system due to the error involved in the projection of latitudes and longitudes from the WGS84 ellipsoid onto a sphere [40]. Distances and angles should not be estimated from Web Mercator maps. [PERSON] et al. [40] provide details on the implications of using Web Mercator in various online map services. The most common standards used in serving pre-rendered or on-the-fly computed map tiles over the internet are the Web Map Service (WMS) and the Web Map Tile Service (WTMS) protocols. The OpenLayers library [41] is a commonly used open-source JavaScript library for interfacing web map services in web applications. OpenLayers requires input of data in WGS84 datum by default [42]. To display data on a web mapping application, the typical workflow involves (i) the transformation of data to WGS84, (ii) the transformation of WGS84 data to the Web Mercator (spherical) projection, and (iii) the display of a map. A number of widely available web map services with global coverage layers are available, including Google Maps, ESRI, Mapbox, Bing Maps, AppleMaps, OpenStreetMap, and Mapquest. [PERSON] et al. [43] reviewed the technical specifications of Google Earth,while [PERSON] et al. [44] reported on the spatial and temporal availability of imagery in Google Earth and Bing Maps. As mentioned earlier, Chinese web map service providers are required to use obfuscated GCJ02 [25]. The popular provider Beiduo Maps adds a further obfuscation to GCJ-02, termed BD-09, to prevent competitors from accessing Beiduo's data [45]. The Google Maps service is particularly popular, including in scientific and technical applications [46] due to its availability at higher resolutions (to 15 cm where aerial imagery has been used) and relatively higher currency (imaging dates).