Digital ballot images
This is a policy brief from Voting Booth on digital ballot images and their role in tabulating and verifying election results.
From the executive summary:
Digital ballot images are one data set among essential records used by election officials and election computer systems to tabulate and verify votes. While most Americans now vote on hand- marked or machine-marked paper ballots, the tabulation process in most jurisdictions is electronic. That process starts with a scanner creating a screenshot of every side of every paper ballot card, which is called a digital ballot image. Both computer software and human election workers analyze and examine ballot images to determine voter intent and to tally votes.
Ballot images have been used across the U.S. by county and state elections officials in recent years in a number of ways. They help to find and fix tabulation errors before the election results are certified, such as a scanner pulling two ballot cards through at the same time. They are used in comprehensive official and unofficial audits before certification, including sharing them with campaigns to determine if recounts and election challenges will be fruitful. Ballot images have been posted online as evidence for the public. Democrats and Republican officials have used ballot images this way in Maryland, Florida, California, Colorado, and other states.
As useful as ballot images may be, they are insufficient to verify results. Ballot images must be compared with other key data for consistency across the tabulation process. Ballot images are the starting line of the electronic tabulation process. The finish line is a large electronic database file of every vote cast on every ballot called the cast vote record (CVR). The CVR is annotated when election workers determine a voter’s intent on a sloppily marked ballot or if other issues arise, such as remaking a spoiled ballot. If necessary, the actual physical ballot can be examined by election boards for further evaluation of tabulation accuracy.