TitleBodyTechnical Expertise RequiredCostAdditional Information
Consider the compatibility of the data you are integrating

The integration of multiple data sets from different sources requires that they be compatible. Methods used to create the data should be considered early in the process, to avoid problems later during attempts to integrate data sets. Note that just because data can be integrated does not necessarily mean that they should be, or that the final product can meet the needs of the study. Where possible, clearly state situations or conditions where it is and is not appropriate to use your data, and provide information (such as software used and good metadata) to make integration easier.

Create a data dictionary

A data dictionary provides a detailed description for each element or variable in your dataset and data model. Data dictionaries are used to document important and useful information such as a descriptive name, the data type, allowed values, units, and text description. A data dictionary provides a concise guide to understanding and using the data.

Document steps used in data processing

Different types of new data may be created in the course of a project, for instance visualizations, plots, statistical outputs, a new dataset created by integrating multiple datasets, etc. Whenever possible, document your workflow (the process used to clean, analyze and visualize data) noting what data products are created at each step. Depending on the nature of the project, this might be as a computer script, or it may be notes in a text file documenting the process you used (i.e. process metadata). If workflows are preserved along with data products, they can be executed and enable the data product to be reproduced.

Double-check the data you enter

Ensuring accuracy of your data is critical to any analysis that follows.

When transcribing data from paper records to digital representation, have at least two, but preferably more people transcribe the same data, and compare resulting digital files. At a minimum someone other than the person who originally entered the data should compare the paper records to the digital file. Disagreements can then be flagged and resolved.

In addition to transcription accuracy, data compiled from multiple sources may need review or evaluation. For instance, citizen science records such as bird photographs may have taxonomic identification that an expert may need to review and potentially revise.

Mark data with quality control flags

As part of any review or quality assurance of data, potential problems can be categorized systematically. For example data can be labeled as 0 for unexamined, -1 for potential problems and 1 for "good data." Some research communities have developed standard protocols; check with others in your discipline to determine if standards for data flagging already exist.

The marine community has many examples of quality control flags that can be found on the web. There does not yet seem to be standards across the marine or terrestrial communities.

Understand the geospatial parameters of multiple data sources

Understand the input geospatial data parameters, including scale, map projection, geographic datum, and resolution, when integrating data from multiple sources. Care should be taken to ensure that the geospatial parameters of the source datasets can be legitimately combined. If working with raster data, consider the data type of the raster cell values as well as if the raster data represent discrete or continuous values. If working with vector data, consider feature representation (e.g., points, polygons, lines). It may be necessary to re-project your source data into one common projection appropriate to your intended analysis. Data product quality degradation or loss of data product utility can result when combining geospatial data that contain incompatible geospatial parameters. Spatial analysis of a dataset created from combining data having considerably different scales or map projections may result in erroneous results.

Document the geospatial parameters of any output dataset derived from combining multiple data products. Include this information in the final data product's metadata as part of the product's provenance or origin.