Source Data
Areas With Existing Ownership Mapping from Teranet
Areas Without Existing Ownership Mapping from Teranet

Source Data

The source data used to produce the Ontario Parcel mapping varies from area to area depending on whether or not digital ownership mapping has been produced by Teranet. Teranet has produced digital ownership mapping, which covers about 65% of the assessment parcels digitized from the Municipal Property Assessment Corporation (MPAC) mapping for the Ontario Parcel mapping. Since the relationship between ownership and assessment parcels is one to one for over 80% of all parcels, assembling digital assessment mapping from existing digital ownership mapping is relatively straightforward. In areas where Teranet does not have digital ownership mapping, a wider and more diverse range of source data is required. To accommodate these differences in source materials, two distinct build procedures were employed to produce the Ontario Parcel mapping

Areas With Existing Ownership Mapping from Teranet

Overview

In areas where digital ownership mapping already exists, the build procedure consists of taking that fabric and modifying it as necessary to create an assessment fabric.

Source Material

Source material for this procedure is provided by Teranet and MPAC.

Teranet provides:

• Digital copies of the existing ownership fabric and digital maps showing the division of the area into map blocks;

• A digital subset of the POLARIS (Province of Ontario Land Registration Information System) title data.

MPAC provides:

• Paper copies of existing assessment mapping together with paper copies of plans and sketches where required;

• A digital subset of the OASYS (Ontario Assessment System) attribute data.

Build Procedure

The first step in the procedure consists of scanning and cataloguing the assessment maps and any supporting plans, etc. These materials are then scaled, rotated and moved so that they correctly overlay the digital Teranet ownership fabric.

Software is then used to compare the OASYS attribute records and the POLARIS title records for a single Teranet map block. Depending on how many, an initial relationship is established between PINs (property identification numbers) and ARNs (assessment roll numbers). A rating, a number from 0 to 9, is then assigned to each PIN–ARN relationship.

All relationships with a low rating are visually examined by comparing the ownership map, the assessment map, the title data and the OASYS data. This results in some adjustments to the relationships and their ratings.

The next step is to create the digital assessment fabric. The digital ownership fabric is the starting point for this exercise. For the most part, ownership boundaries become assessment boundaries. In cases where the PIN–ARN relationship is not one to one, a comparison of the data allows determination of where boundaries need to be added or deleted to create the assessment fabric.

In cases where there is a one-to-one relationship between a PIN and an ARN, and where that relationship has a high rating, the ARN is placed into the digital map file. In other cases, visual examination of the source data and reference to the ARN interpretation guidelines provided by MPAC enable a determination to be made as to the likely ARN for a given parcel.

Limitations of the Build Procedure

The product resulting from any procedure of this nature is only as good as the source material. One of the limitations of the source material is that each of the four data sources is on a different maintenance cycle. This, along with inconsistencies in the source data, can produce discrepancies between PIN and ARN and between map and attribute data, which would not be present if all four sources of data had the same currency and consistency.

The accuracy of the digital assessment mapping is only as good as the accuracy of the underlying Teranet ownership mapping. The accuracy of this mapping varies between urban areas mapped using the POLARIS standard and rural areas where the mapping has been based on 1:10,000 topographic mapping with limited use of survey data.

Overview

The build procedure for areas where Teranet did not provide digital ownership mapping consists of assembling both assessment and Crown parcel mapping on the Ministry of Natural Resources (MNR) digital topographic and township base maps.

Source Material

Source material for this procedure is provided by MPAC, MNR and Teranet.

MPAC provides:

• Paper copies of existing assessment mapping together with paper copies of plans and sketches where required ;

• A digital subset of the OASYS attribute data.

MNR provides:

• Digital topographic and township data (provincial NRVIS [Natural Resources and Values Information System] or federal NTS [National Topographic Series]);

• Paper copies of supporting information on the township fabric;

• Information from the Ministry's Geographic Township Improvement Program;

• Digital data defining the official names for topographic features (Ontario Geographic Names Database);

• Digital data for many Crown parcels (ClaiMaps II);

• Paper copies of T, G and M plans showing other Crown parcels.

Teranet provides:

• Digital copies of the existing ownership fabric for areas that are adjacent to the area to be mapped.

Build Procedure

The first step in the build procedure involved an objective evaluation of the quality of the township fabric data supplied by MNR. Depending on the severity of problems found, the action taken varied from making minor adjustments to complete reconstruction of part of the fabric.

Once this stage was completed, the source material for assessment and Crown parcels is evaluated on an area-by-area basis. The most accurate material will be used first. So in some cases the Crown parcel fabric could be built before the assessment parcel fabric and vice versa.
As parcels were created from the source material, they may have been adjusted to make them fit the topographic and township base.

As the second set of parcels was created, they were adjusted, where necessary, to fit the first set of parcels. In some cases a parcel shown on an assessment map may not obviously appear to represent the same physical area as a parcel shown on an MNR map. In such cases if the evidence suggests that they are physically the same, then the definition of the second parcel was made to be identical to the definition of the first parcel. If the evidence is not clear, two distinct parcels were created as shown on the two sources of data.

Where two adjacent assessment parcels were shown with the same ARN in the source data, they were merged into a single parcel.

In some areas where all or most land has been alienated from the Crown, and where MNR has no source data for Crown parcels, Crown parcels were constructed using the overall pattern of the assessment parcels. This frequently resulted in half-lot or full-lot Crown parcels.

In some areas, assessment and Crown parcels were indicated by a single point in the source material. In such cases, an arbitrary 20-metre square shape was created to represent the parcel. Care was be taken to ensure that such parcels do not overlap other parcels.

ARN text were placed based on what is shown in the source material and on ARN interpretation guidelines provided by MPAC. In the case of Crown parcels, identifier text were assigned to the parcel using the next available number from a list provided by MNR. Other text was added as shown in the source material.

Limitations of the Build Procedure

The product resulting from any procedure of this nature is only as good as the source material. A major limitation of the source data is the lack of a direct cross-reference between assessment and Crown parcel source data. The fact that these records were created to different scales with differing degrees of accuracy often makes it difficult to determine if a parcel shown on both maps is or is not the same physical entity.

The lack of consistency in source material can also make it difficult to correctly interpret the source material.

The largest scale of “MNR’s” topographic and township data is 1:10,000 and this limits the quality of the final product. In more northern areas, the scales are even smaller. In addition, some of “MNR’s” digital topographic data is actually second generation, having been created by digitizing mylar Ontario Base Maps.

Very limited reference is made to survey data during the assembling of the assessment and Crown parcels. Existing assessment and Crown parcel mapping in the source material was created by a variety of methods and to a variety of standards. Its quality varies significantly.

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