#Utm zones usa how to#
#Utm zones usa software#
#Utm zones usa iso#

#Utm zones usa iso#

This is detailed in a 100+ page document that “defines the structure and content of a text string implementation of the abstract model for coordinate reference systems described in ISO 19111:2019” ( Open Geospatial Consortium 2019). The longer answer is that none of the three descriptions are sufficient and more detail is needed for unambiguous CRS handling and transformations: due to the complexity of CRSs, it is not possible to capture all relevant information about them in such short text strings.įor this reason, the Open Geospatial Consortium (OGC, which also developed the simple features specification that the sf package implements) developed an open standard format for describing CRSs that is called WKT (Well Known Text). The more concise identifier 4326 is understood by sf, but we recommend the more explicit AUTHORITY:CODE representation to prevent ambiguity and to provide context.

#Utm zones usa software#

The short answer is that the third way to identify CRSs is correct: EPSG:4326 is understood by sf (and by extension stars) and terra packages covered in this book, plus many other software projects for working with geographic data including QGIS and PROJ.įurthermore, although it is machine readable, unlike the proj-string representation “EPSG:4326” is short, easy to remember and highly ‘findable’ online (searching for EPSG:4326 yields a dedicated page on the website epsg.io, for example).

With an identifying ‘authority:code’ text string such as EPSG:4326.Įach refers to the same thing: the ‘WGS84’ coordinate system that forms the basis of Global Positioning System (GPS) coordinates and many other datasets.

Formalized yet now outdated ‘proj4 strings’ such as +proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs.

Simple yet potentially ambiguous statements such as “it’s in lon/lat coordinates”.

Most modern geographic tools that require CRS conversions, including core R-spatial packages and desktop GIS software such as QGIS, interface with PROJ, an open source C++ library that “transforms coordinates from one coordinate reference system (CRS) to another”.ĬRSs can be described in many ways, including the following. We cover reprojecting vector and raster objects in sections 7.7 and 7.8 and modifying map projections in Section 7.9. We tackle questions of when to reproject and which CRS to use in Section 7.5 and Section 7.6, respectively. Section 7.4 demonstrates the importance of knowing what CRS your data is in with reference to a worked example of creating buffers.

#Utm zones usa how to#

In the next section we introduce CRSs in R, followed by Section 7.3 which shows how to get and set CRSs associated with spatial objects. This chapter teaches the fundamentals of CRSs, demonstrates the consequences of using different CRSs (including what can go wrong), and how to ‘reproject’ datasets from one coordinate system to another. Having a clearly defined project CRS that all project data is in, plus understanding how and why to use different CRSs, can ensure that things don’t go wrong.įurthermore, learning about coordinate systems will deepen your knowledge of geographic datasets and how to use them effectively. However, if you know the CRS of your data and the consequences for geometry operations (covered in the next section), CRSs should just work behind the scenes: people often suddenly need to learn about CRSs when things go wrong. It is important to know if your data is in a projected or geographic coordinate system, and the consequences of this for geometry operations. In many projects there is no need to worry about, let alone convert between, different CRSs. It demonstrates how to set and transform geographic data from one CRS to another and, furthermore, highlights specific issues that can arise due to ignoring CRSs that you should be aware of, especially if your data is stored with lon/lat coordinates. This chapter builds on that knowledge and goes further.

Section 2.4 introduced coordinate reference systems (CRSs), with a focus on the two major types: geographic (‘lon/lat’, with units in degrees longitude and latitude) and projected (typically with units of meters from a datum) coordinate systems.