ALS News: From the DPR - Plan Checking 101 – Closures and Two Other Key Plan Examination Steps

Scott Westlund, ALS, Director of Practice Review

I didn’t want, or think I needed, to write this article. Over the past five years, the number of plans I’ve examined that contain more than three obvious drafting errors has reduced by more than half. As presented in my CCR Phase 2 Final Report, 51% of the plans I examined in Phase 1 had more than three drafting errors, and in Phase 2, 19% of the plans I examined had more than three drafting errors. I was very pleased to see this drastic reduction because drafting errors were the most common deficiency identified during Phase 1. Indeed, while conducting Phase 2 reviews I noticed that many ALSs improved their plan preparation and checking processes between Phase 1 and Phase 2. This is commendable. I like to think improvements were made in response to our rigorous review process but I realize that processes were more likely improved to increase efficiency and because no one wants to make drafting errors.

As we approach the end of CCR Phase 3, I am pleased to report that the downward trend for drafting errors continues. To date, I’ve examined 319 plans in Phase 3, and I found that 41 of them had more than three drafting errors (13%). This is great but I think we can do better. Of these 41 plans, 18 didn’t close. Indeed, in the past few weeks, I’ve examined three plans that didn’t close. In each case, the misclosure was the result of an obvious drafting error that I detected during my plan examination. I’ve highlighted the benefits of doing a plan closure several times in various articles over the years and I’ll do it again here. Additionally, using three real examples (sanitized), I’ll demonstrate the three key plan checking steps I use to detect and identify drafting errors that cause a misclosure. I believe that if these three steps are taken during every ALS’s own plan examination, I will not find another plan that doesn’t close. That is what I hope to report for Phase 4!

Step 1 - Closures
The first thing I do when I examine a plan is open my MicroSurvey and work my way around the plan to make sure it closes. I find that computing a plan closure is a very effective error detection tool and doing this step first helps me understand what else I may need to look out for. For example, while doing the closure I also notice if dimensions are missing, see unusual evidence descriptions (e.g., restored monuments identified as re-established), incorrect lot and block labels, interesting re-establishment methodologies, curve data that is difficult to use, and details that don’t match the body of the plan. Based on what I see while conducting reviews, a plan closure is a critical step that should be part of every plan checking process. Indeed, Part D Section 1.5 of the Manual of Standard Practice states:

Figure 1 shows the south easterly portion of a large subdivision plan registered under Section 47. The first thing I do when I examine a large subdivision plan is compute a closure around the perimeter and then work my way through the interior lots. In this example, I happened to start my closure in the NW corner of the plan and when I got back to the starting point, I found an 11 metre misclosure. Of course, when seeing a misclosure of this magnitude, I immediately thought that I’d made an error, or I entered one of the curves in the wrong direction. To ensure it wasn’t my error I methodically selected each line segment to compare what I entered to the information on the plan. When I confirmed that I entered everything as per the plan, I went on to Step 2 in my process to find the error (I inversed between coordinates in the published coordinate table for positions on the perimeter).

In this case, it turned out that the distance shown as 38.89 is actually between points 603 and 604 and the distance between point 202 and 603 is 27.25. It seems likely that point 202 and the other points to the southeast of this were added to the plan after the plan was initially dimensioned and the dimensions were not updated to reflect the new information.

As a side note, the area bounded by point 202, 203, 204 and 605 is depicted on a right-of-way plan that was registered at the same time as the subdivision plan. I think the point numbers and dimensions associated with this right-of-way could have been left off of the subdivision plan and placed on the right-of-way plan so that the right-of-way plan stands alone. Including point 202 on the subdivision plan means that the subdivision perimeter is defined by point 202. This could cause confusion because a posting error at point 202 would introduce a deflection in the subdivision perimeter. I think that if point 202 is supposed to govern the location of a right-of-way, it should be shown as placed on a right-of-way plan.

Figure 1 – Large Subdivision Plan Example

Step 2 – Comparing distances and bearings on the plan to the inverses calculated from the coordinates in the ASCII file
My second plan examination step involves importing the ASCII coordinates (after I convert them to ground in Excel) into MicroSurvey and querying the inverse between adjacent points to confirm the information shown on the plan matches the inverses. As noted above in my subdivision example, I imported the coordinates published in the Section 47 coordinate table for the inverses. When I examined the hybrid cadastre plan shown in Figure 2, Step 1of my plan examination process revealed that the plan didn’t close by 0.8 and, in this case, I manually typed the governing coordinates from the hybrid cadastre table of coordinate into Excel, converted them to ground (there were only 14 that I needed), and imported them into MicroSurvey to do inverses.

According to the coordinates shown in the table, the inverse between Point 22 and Point 20 is 335°52'01" 49.137. Since this doesn’t match what is shown on the plan, I think I know which dimension caused the misclosure but I’m not exactly sure why this dimension is incorrect. It could be that the coordinate in the table for point 20 or 22 is incorrect (it doesn’t seem like it because the inverses between Point 21 and 20 and 22 and 23 match what is shown on the plan) or the line has been inadvertently dimensioned to another point that is south of point 20 (I didn’t see one). At this point, I have left it to the ALS who prepared the plan to figure it out.

A plan misclosure clearly indicates that further investigation into the dimensions on the plan is necessary and I think it goes without saying that any errors should be corrected before a plan is issued.

Figure 2 – Hybrid Cadastre Plan Example

Step 3 – Comparing the information shown on the plan to the field notes
My next plan examination step is to compare the information shown on the plan to what is shown in the field notes. This step often reveals discrepancies in evidence descriptions (found v. placed or re-established v. restored), dimensions that are to an incorrect position (e.g., another post or a random line intersection in close proximity), posts that were placed incorrectly or have not been placed, and incorrect dimensions around posts that are actually reference posts. For this example, I pieced together the information in Figure 3 from a one lot subdivision plan. I was unable to compute a closure for this figure using the information shown on the plan because there is no bearing or angle connecting ASCM 2 to ASCM 5 or ASCM 5 to ASCM 9. Although, as per the Manual of Standard Practice Part C Section 7.1.2, markers should be connected, it is not uncommon to have to consult the ASCM card for information to compute a closure through ASCMs. What I found unusual in this case was that when I pulled the ASCM card for ASCM 2 it showed that ASCM 2 was reported destroyed in the 1980s. This caught my attention and when I reviewed the field notes, I could not find any evidence that ASCM 2 was found or surveyed as part of this survey. ASCM 2 should not have been shown on the plan.

On a side note, if ASCM 2 was to actually exist, I think the distances shown from the NE 22 to ASCM 2 and from ASCM 2 to ASCM 5 are incorrect by about 200 metres and 35 metres respectively. I think a grid coordinate for ASCM 2 may have been inadvertently inserted into a ground version of the drawing and it was incorporated into the plan for some unknown reason.
Figure 3 – One Lot Subdivision Plan Example

Drafting errors can increase liability, create ambiguity, cause confusion and can sometimes lead to boundary uncertainty. Not to mention that it’s embarrassing to get a call from another ALS about a drafting error. Reducing drafting errors protects the public, improves our products, reduces the number of corrections, and increases confidence in surveys. As mentioned, if these three simple steps are taken as part of every plan checking process, I think we could further cut the number of drafting errors in half.