CRS in Petrosys

What is a Coordinate Reference System?

Maps are an effective way of communicating large volumes of information quickly and concisely. Maps show the audience where things are located in reference to each other. How can we know that the spatial conditions on the map reflect reality? It is through the correct use of the coordinate reference systems (CRS) that we can accurately display objects from a three dimensional world on a two dimensional piece of paper (or computer screen).

There are two types of CRS that are widely used when creating maps: geographic CRS and projected CRS. A geographic CRS is defined by simplifying the overall shape of the Earth, orienting this simplified “spheroid” in space, and applying a set of polar coordinates to the “spheroid.” Now when you use latitude and longitude to define a point on a map you are using a specific geographic CRS.

A projected CRS can be defined by projecting the 3D surface onto a 2 dimensional plane (such as a computer screen or flat paper map). Projected coordinate reference systems are used to apply a set of Cartesian coordinates to the Earth’s surface. This allows the mapmaker to use a pair of X and Y coordinates to indicate a specific location on the planet. There are many different ways of projecting the 3D surface onto a 2D plane. The different methods of projection affect the accuracy of maps with regards to distance and area. Different projected CRSs will be used over different areas and for different uses. Some are very accurate over small areas and others sacrifice small scale accuracy so they may limit distortion over large regions.

How does Petrosys use CRS?

Petrosys software is CRS aware, this means that any operation completed within Petrosys will have taken CRS into account. If you create a surface model (grid) it will be created using a specified projected CRS, when you display data on a map everything is displayed utilizing valid CRS definitions. One of the many benefits of using Petrosys is the powerful CRS engine always running in the background.

End users only need to specify the desired output CRS and Petrosys runs any transformations in the background. Petrosys will display data from multiple projected CRSs in the correct location for the user specified target CRS. In the same way, Petrosys gridding and contouring will take input data sets from a variety of CRSs and create realistic models in a single target CRS.

Petrosys multi-connect technology allows live connections to many data sources and handles multiple source CRSs on the fly. Petrosys identifies source CRS through variety of interrogation techniques that make working in Petrosys simple for the end user. These methods include reading well known text within individual files, accessing common associated files that contain projection information, running database queries that directly access CRS information from the external data source. Once Petrosys determines the source CRS all coordinates are transformed into the user specified target CRS.

The state-of-the-art Petrosys CRS engine utilizes industry standard CRS definitions from the EPSG. These definitions include commonly used transformation methods that allow geographic coordinates to be transformed to other geographic CRSs. Data can easily be displayed in a variety of CRSs by switching from one Petrosys map sheet to another. All data being displayed will automatically be shown using the projected CRS set in the map sheet.

Why should I care about CRS?

There are a myriad of problems that can occur when the wrong CRS is used. These problems can manifest themselves as incorrect distance measurements, invalid area reporting, wrong locations, etc. Using the wrong geographic CRS can show a well hundreds of feet from where it is really located. Using the wrong projected CRS can cause a grid that should be in the Gulf of Mexico to display in the Arctic Circle. These are examples of glaring problems but less obvious problems can arise if the wrong CRS is used.

Geographic and projected CRSs are extremely important topics that have been around from the time accurate maps started being drawn. This article barely scratches the surface of this complex subject and anyone with an interest should look for further information.

We all want to make the most accurate maps possible and to do so you have to think about proper CRS handling. Petrosys makes this easy by automatically reading source CRS and doing on-the-fly transformations to target CRS.