What File Format Should I Export from Surfer?

Surfer supports exporting to many different file formats. When exporting data from Surfer for use either in another software package (either another Golden Software package or a third-party application), for inserting into a publication, or for any other purpose, the multitude of supported file formats can be confusing. It may not always be clear when you should be using the Golden Software file types (e.g. BLN, GSB, GSI, etc) or another file format (e.g. DXF, SHP, MIF), or when you need another file format altogether.

There are three main types of files you can export or save from Surfer: grid files, data files, and base map files. The base map file formats can be further subdivided into three types, raster image, vector and metafile formats. Which format you choose to export depends on what you are exporting, and what you want to do with the exported data.

1. Grid Files (e.g. ADF, ASC, DEM, GRD)
2. Data Files (e.g., CSV, DAT, TXT, XLSX)
3. Base Map Files
3a. Raster Image     (e.g. BMP, JPG, GeoTIFF, TIF)
3b. Vector     (e.g. E00, DXF, KML, MIF, SHP)
3c. Metafile     (e.g. EMF, WMF)

Grid and data file formats are fairly self-explanatory with little variation in the content in these files. This article will not focus on these formats, but give some brief information:

• Grid files contain XY extents in map units, grid spacing, Z values at grid nodes (or grid cell centers, depending on the grid file format), and null values. There is not much variation in the information saved to these types of files. You could save a grid from Surfer to create contours, watersheds, or other map types in Surfer or other applications, or perform other grid calculations such as math or volume operations. The X, Y and Z information is the same in all grid formats, so the format you choose depends on the supported file formats of the program with which the grid will be used. For example, if you work primarily in Surfer, save grids in the default Surfer grid file format. If you want to bring the grids into ArcMap for display, save the grids in one of the supported ESRI grid formats (e.g. ADF, ASC or FLT).
• Data files contain raw data. Data files can be Excel spreadsheets, TXT or other ASCII data files. They can contain XY information along with Z values, labels, or other data. Again, there is not much variation as all of the data files contain the same basic information. You can save a data file from the Surfer worksheet in many different formats, including CSV, DAT or XLSX. The data saved will be the same in all formats. The only formats that may have a difference are the Excel formats if you have many thousands of rows of data. This is because the Excel formats are limited to a certain number of rows and columns:
  • XLS file format is limited to a 65536 rows and 256 columns
  • XLSX is limited to 1,048,576 rows and 16,384 columns

This article will focus primarily on the variations in the various base map file formats. As mentioned previously, the base map file formats can be further subdivided into three types: raster image files, vector files, and metafiles.

Raster Image Files

Raster images are images of exactly what you see on the screen. This type of file is a good option for sending a picture of the map to a colleague, inserting the image into a report or presentation, uploading the image to a website, or sending the image to a publication for print. This is also a good choice if you need a georeferenced image to overlay with other map types either in Surfer or other applications. Normally individual elements are not editable in raster image file formats. So, line styles, line widths and text properties are not editable. Some options, such as color, are editable using image processing software.

Similar to grid and data files, there is little variation in the actual content of these files. A picture of what is in your Surfer project file is exported. The main differences between formats are some of the format-specific options. Which format you choose depends on if you need compression, background transparency, or what format you are required to provide (if you are going to use it in another application or for publication).

All the image export formats support options for setting the pixel size, resolution (e.g. dpi), document size, and color format for the exported image. In addition, all image formats have the option to include spatial reference information, such as real world XY coordinates and coordinate system (e.g. projection/datum) information.

The spatial reference information can be saved in a number of formats, including an internal only format (e.g. GeoTIFF), or in external files, such as:

• Blue Marble .RSF file
• ESRI World file (.xxW)
• ESRI .PRJ file
• Golden Software Reference (.GSR and .GSR2) files

Note that the Blue Marble RSF and ESRI World files only contain XY coordinate information. They do not contain any coordinate system information. Likewise, the ESRI PRJ files only contain coordinate system information and no XY coordinate referencing. Golden Software Reference files contain both real world XY coordinate and coordinate system information.

The following table summarizes the format specific options and provides hints, tips, and cautions for each of the raster image file formats available to export from Surfer.