Science is a business for most of us and credibility in the data we provide our consumers is critical to confidence and success. When it comes to the data we put on maps or use for analytics we know that no credible source equals no faith in the data.
Well data is a great example. In some states you have one governing body managing the oil wells and another governing body managing the gas wells. Neither talk to each other, and both use different unique identifiers. How do you match the wells? On top of that, you must keep the data up to date while still managing quality control, consistency, data models and attribute data.
Land grid data can be a little easier to prove, at least in the PLSS states. In the PLSS states, you can use the USGS 1:24k topo maps to check the accuracy of your land grid. In Texas, it is a lot more challenging. There are two competing sources who do not match perfectly, one of which is the Railroad Commission and the other the General Land Office, which seems to use the Tobin land grid. Like well data, land grid attribute data and the data model are an important part of understanding the science and completeness of the data.
Tax Parcel data tends to fall directly in the hands of individual county and parish assessor offices. Unfortunately, most of these individual counties do not communicate and have very different data models. Luckily, over the last few years states have played a more prominent role and, in some cases, provide data for the whole state within a consistent data model. There are also still some counties and parishes where no vector data is available, only hard copy maps.
Good data vendors simplify the process when it comes to trusted sources and credibility. They do the heavy lifting for you by matching and cross-checking data, creating consistent data models, and by using smarts and external sources where most folks do not have access.
Even with a good data vendor it is still important for you to know the original source of the data you are using. By knowing those sources and by being able to quickly check data on the go, you will have the confidence to present your data and your maps with spatial confidence and accuracy.