Managing points with duplicate names

The Trimble Access software includes a dynamic database. This stores networks of connected vectors during RTK and conventional surveys, making the positions of some points dependent on the positions of others. If you change the coordinates of a point that has dependent vectors (for example, an instrument station, a backsight point, or a GNSS base station), this affects the coordinates of all points that depend on it.

The software uses database search rules to resolve the coordinates of dependent points, based on the new coordinates for a point they depend on. If the coordinates of a point with dependent points move by a certain amount, the dependent points are shifted by the same amount.

When two points of the same name exist, the software uses search rules to determine the best point.

The software lets multiple points with the same point name (point ID) exist in the same job.

To distinguish between points of the same name and to decide how these points are to be used, the software applies a set of search rules. When you ask for the coordinates of a point in order to perform a function or calculation, these search rules examine the database according to:

• the order in which the point records were written to the database
• the classification (search class) given to each point

Order in the database

A database search starts at the beginning of the job database and works down to the end of the job, looking for a point with the specified name.

The software finds the first occurrence of a point of that name. It then searches the rest of the database for points of the same name.

The rules generally followed by the software are:

• If two or more points have the same class and the same name, it uses the first point.
• If two or more points have the same name but different classes, it uses the point of higher class, even if this is not the first occurrence of the point.
• If two or more points (one from the job database and one from an attached linked file) have the same name, the software uses the point in the job database, regardless of the classification of the point in the linked file. However, you can add points to a stakeout list from the linked file using the Select from file option, and the point from the linked file will be used even when the point already exists in the current job. For more information, see Linked files and their search rules.

Search class

The software gives most Coordinates and Observations a classification. It uses this classification to determine the relative importance of points and observations stored in the job database.

Coordinates have priority over Observations. If a Coordinate and an Observation of the same name have the same class, the Coordinate will be used regardless of its order in the database.

Coordinate classes

The Coordinate Classes are arranged in a descending hierarchy, as follows:

• Control – (the highest class) can only be set when a point is keyed in or transferred.
• Averaged – is given to grid positions stored as a result of an average position computation.
• Adjusted – is given to points that are adjusted in a traverse computation.
• Normal – is given to keyed‑in and copied points.
• Construction – is given to all points measured using Fastfix, which are typically used in the computation of another point.
• Deleted – is given to points that have been overwritten, where the original point had the same (or a lower) search class than the new point.

Deleted points are not displayed in point lists and they are not used in calculations. However, they do remain in the database.

Control class

Control class is used in preference to other coordinate classes. It can only be set by you. Use control class for points that you want to use in preference to points of the same name in the same job database. See Assigning control class to a point.

You cannot overwrite a control class point with a measured point, or use a control class point in an average position computation.

In general, if there are multiple observations with the same name, the best point is determined by the point that has the highest classification.

Observation classes

The Observation Classes are arranged in a descending hierarchy, as follows:

• Mean Turned Angle (MTA) *, Normal, Backsight, and Stakeout
• Construction
• Check
• Deleted

Deleted observations are not displayed in point lists and they are not used in calculations. However, they do remain in the database.

If there are multiple observations of the same name which also have an equivalent classification (that is, normal and backsight are equivalent), then the best is the one that is found first in the database.

* Within a single station setup, a Mean Turned Angle observation is better than all the other classes – it is treated as an equivalent classification to the other classifications that are listed only when the observations appear in different station setups.

Example

If a point named "1000" is entered as the start point when calculating a from‑a‑baseline offset, the software searches for the first occurrence of point "1000". It then searches the rest of the database for any point named "1000", under the following rules:

• If no other point of this name is found, it uses the one it has to calculate the offset.
• If another point "1000" is found, the software compares the classes of the two points. It uses the point "1000" that has the highest classification. Remember that a Coordinate class point (for example, keyed‑in) is higher than an Observation class point.

For example, if both points were keyed in, one was given a normal classification and the other a control classification, Trimble Access uses the control class point to calculate the offset, regardless of which record the search finds first. If one point was keyed in and one was observed, Trimble Access uses the keyed‑in point.

• If the points are of the same class, Trimble Access uses the first one. For example, if both points named "1000" were keyed in, and both were given a normal classification, the first one is used.

Normal search rules are not used in the following situations:

• In a GNSS calibration

  Calibration searches for the highest class point stored as grid coordinates. This grid point is used as one of a pair of calibration points. The software then searches for the highest class GNSS point stored as Global coordinates or as a Global vector. This point is used as the GNSS part of the point pair.

• When starting an RTK rover

  When you start a rover survey, if the broadcast base point is called, for example, "BASE001", choosing Start survey causes the software to search for the highest class GNSS point of that name stored as Global coordinates. If there is no GNSS point stored as Global coordinates, but "BASE001" exists stored as grid or local coordinates, the software converts the grid or local coordinates of the point into Global coordinates. It uses the projection, datum transformation, and current calibration to calculate the point. It is then stored, as "BASE001", with Global coordinates and is given a check class classification so that the original grid or local coordinates will still be used in calculations.

  The Global coordinates of the base point in the database are the coordinates from which GNSS vectors are solved.

  If there is no base point in the database, the position broadcast by the base receiver is stored as a normal class point and it is used as the base coordinates.

Normal search rules are not used in the following situations:

• Face 1 or face 2 from one station setup and an MTA from another station setup

  If you observe a point on more than one face, the face 1 observation and the face 2 observation are combined to create an MTA record. In this situation, the MTA is used to coordinate the point. However, if there is an observation to a point on face 1 or face 2 only, from an earlier station setup, and later a station setup (that could be at the same station as the first) to that same point creates a new MTA, then the MTA is deemed to be of the same class as the earlier face 1 or face 2 observation. In this situation, the order in the database rule is invoked, and the first point in the database is deemed the best point.

• Observations that coordinate a point are better than those that do not

  An angles and distance observation that coordinates the point, is better than an angles‑only observation that does not coordinate a point. This rule applies even when the angles‑only observation is earlier in the database, and is of a higher class, for example, an MTA.

Comma Delimited (*.csv or *.txt) files or (job) files can be linked to the current job to access external data. See Linked files.

The search rules do not operate across linked files. Points in the current job are always used in preference to a point of the same name in the linked file, regardless of the classification. For example, if point 1000 in the current job has an As‑staked classification, and point 1000 in a linked job file has a Normal coordinate classification, then the search rules will select the As‑staked class point in preference to the Normal class point. If both points were in the current job, then the search rules would select the Normal class point.

You can add points to the stakeout list using the Select from file option even if the point in the linked file already exists in the current job. When a point of the same name exists in the current job, this is the only way that you can stake a point from a linked file.

When points of the same name exist in a single CSV file, the software uses the first point.

When points of the same name exist in multiple CSV files, the software uses the point in the first CSV file. The first CSV file is the first one in the file selection list. To change the order of the CSV files, tap the tabs at the top of the file selection screen. If you change the order of the CSV files, this may change the order in which files are selected.

When you accept a CSV file selection, and you then go back and select more CSV files, all subsequent files are appended to the initial selection, using the rules. This assumes that the original selection is not altered.

Trimble recommends that you do not use multiple CSV files that contain points of the same name.

To find the point with the highest classification, use the Point manager. In the Point manager, the highest class point always appears at the first level in the tree structure. If there is more than one point of the same name, the tree structure has a second level, which contains all points of the same name. The point with the highest classification appears at the top, followed by the other points of the same name, in the order in which they were observed.

Duplicate point tolerance settings are configured in the survey style. When storing points, these settings are used to compare the coordinates of the point to be stored with points of the same name that already exist in the database. If the coordinates are outside the duplicate point tolerances defined in the survey style, the Duplicate point out of tolerance dialog appears.

This warning appears only if the new point is out of tolerance with the original point. If you have changed the tolerance values, the message may not appear. See Duplicate point tolerance options.

Of the options displayed in the Duplicate point out of tolerance dialog, Overwrite and Average are the only two options that might result in a point being 'promoted' – thus changing the coordinates for the best point.

In a conventional survey, observations from one station setup to the same point are combined to create an MTA record. You do not see the "duplicate point out of tolerance" warning.

If you store a face 2 observation to a point that already has a face 1 observation, the face 2 observation is checked to see if it is within tolerance of the face 1 observation and then stored. For more information about face 1 and face 2 observations, see Measuring a point in two faces.

The overwrite rules

Overwrite deletes points, and results in a change to the coordinates of the best point. Deleted points remain in the database and have a search class of Deleted. See Search class.

If the Overwrite option does not appear in the software, this means that an overwrite would not result in changes to the coordinates of the best point.

Select Overwrite to store the new point and delete all existing points of the same class or below:

• Observations can overwrite and therefore delete Observations.
• Coordinates can overwrite and therefore delete Coordinates.
• Observations cannot overwrite Coordinates.
• Coordinates cannot overwrite Observations.

One exception to these rules is when a Rotate, Scale or Translation is performed. When one of these transformations is applied, the original observations are deleted and replaced by the translated points.

That does not mean that all Observations can overwrite all other Observations of the same name, and all Coordinates can overwrite all Coordinates of the same name. The Search class rules still apply.

Overwrite examples

• If you measure a point with a name that already exists in the database, you can choose to overwrite it when you store the new one. All previous Observations of the same name, and with the same or a lower search class, are deleted.

If a point stored as a Coordinate existed, then overwrite would not have been an option, because overwriting the observations would not have changed the best point.

• If you key in a point with a name that already exists in the database, you can choose to overwrite it when you store the new one. All previous points stored as Coordinates, of the same name, and with the same or a lower search class, are deleted. Points of the same name stored as Observations are not affected.

Storing another does not change the best point

If you measure or key in a point with a name that already exists in the database, you can choose to store both points in the database, and both are transferred with the job. The Trimble Access search rules ensure that the point with the highest class is used for calculations. If there are two points of the same class, the first is used.

Averaging overwrites another average

If you measure a point and use a name that already exists in the current job, you can choose to average all points of that name. To store the observation and an averaged grid coordinate, select Average. Where an averaged position of that name already exists, the new averaged position will overwrite the existing averaged position. Averaged points have a coordinate classification. Coordinates have a higher classification than observations, so the stored averaged position is used in preference to any observations. You can also choose to Auto‑average when the point is within tolerance. See Auto average tolerance.

Control class is the highest classification that you can give to a point. Any high‑accuracy point that you use as a fixed standard in a job can be a control point.

If you specify control search class when you key in the coordinates for a point, you can be sure that those coordinates will not change until you key in another point of the same name and the same search class (control) and choose to overwrite the first point.

The Trimble Access software never elevates measured points to control class. This is because measured points have measurement errors and may change or be measured again during the course of the job. If the keyed‑in point "CONTROL29" is control class, generally you would not want the coordinates of that point to change. A control class point is held fixed for the job.

The Trimble Access software can measure observed control points, but it does not give them control classification. This is because, in calibration, the measured point often has the same name as the keyed‑in control point. This makes it easier to set up the calibration. It also makes it easier to manage your data, for example, if you know that all references to point "CONTROL29" on the ground are also references to point "CONTROL29" in the database.