Before You Establish Anything: Is There Already a Known Point?
Every method in the chapters ahead solves the same problem: giving a new base station a trustworthy coordinate. The fastest way to solve that problem is sometimes to skip it entirely, by occupying a point whose coordinate someone else already established.
If a published monument or a prior control point already exists near a project, occupying it can skip the entire process of establishing a new coordinate. That option is not a faster version of the methods ahead. It is a way to bypass them altogether, when it is available.
Inheriting an Accuracy You Did Not Have to Earn
A well-established published monument may carry an accuracy no quick method in this companion could match on its own, since it was very possibly established using exactly the rigorous techniques this companion covers later, by someone else, at some point in the past. Occupying that point and using its published coordinate directly inherits all of that prior effort, at essentially no cost beyond finding the point and setting up over it correctly.
A known point does not sit on this companion's accuracy ladder at all. Its accuracy is whatever was already invested in establishing it, which can be far better, or occasionally worse, than any single method covered in the chapters ahead.
The Metadata Discipline This Series Keeps Returning To
A published coordinate is only as useful as everything known about it beyond the number itself. Which reference frame it belongs to, which specific realization of that frame, and which epoch it was established at, all matter exactly as much here as they have mattered throughout this series. Entering a known coordinate without confirming that context is not a shortcut. It is a way to silently import a reference frame mismatch before a single satellite observation has even been taken.
A known, published coordinate is not automatically safe to use just because it came from a trusted source. Without confirming its reference frame, realization, and epoch, occupying it can introduce exactly the kind of frame mismatch this series has warned about from its very first companion.
When This Option Simply Is Not Available
Plenty of projects have no known point anywhere nearby worth using, and that is precisely when the methods in the chapters ahead earn their place. This chapter is not a requirement to satisfy before moving on. It is a single, cheap question worth asking first: does a shortcut already exist, before building the coordinate from scratch.
A published monument sits within reach of a project site, and a crew is debating whether to survey-in a new base point instead. Is starting from scratch ever the better choice here? Rarely, provided the monument's frame, realization, and epoch have been confirmed. Occupying an already-established point is usually the better use of the crew's time.
Occupying a known, published point can skip the entire process of establishing a new base coordinate, inheriting whatever accuracy was already invested in that point, provided its reference frame, realization, and epoch are confirmed first. When no such point exists, the methods that follow are what actually establish a coordinate from nothing.
With that shortcut ruled in or out, this companion turns to the full range of methods for establishing a coordinate when no known point is available. The seven tiers ahead are ordered by increasing accuracy, from fastest to most rigorous, but they are alternatives to choose between, not a sequence to complete in full. A given project picks the one tier that actually matches its needs, not all seven in order.