NRSC 2230 / GEOG 2750

GIS Data Input sub-system

Overview

The overall GIS can be broken down into four main sub-systems.  These are the Input sub-system, the Data Management sub-system, the Analysis sub-system and the Output sub-system.  This module will examine the main concerns associated with the Input sub-system.  The other sub-systems will be examined later.

Learning Outcomes

Upon successful completion of this topic, you will be able to:

  • Explain the overall issues involved in evaluating data
  • Explain the issues involved in evaluating spatial data

Overall Data Concerns

The following are some general concerns as they relate to all data:

* currency (date of collection)

* reliability (how data generated and by whom)

* availability ( public domain, confidential)

* coverage and completeness ( all relevant issues covered, all spatial areas covered, reasonable time series)

* logical consistency (results hold up to scrutiny)

* correctness ( a true reflection of reality)

* validity (falls within an acceptable range of values)

* maintainability (ease of update etc.)

Spatial Data concerns

The following are some concerns as they relate to spatial data

* positional accuracy (free of error or bias)

* scale and resolution (precision or the ability to distinguish small differences)

* coordinate system used

* projection

* datum

Note:

When acquiring data from any source, it is important to read the information known as the metadata. This is information about the data and you can address many of the areas of concern listed above.

Activity 1 – Reviewing Source Metadata

The following link provides information about data available from a Government operated site.  Please read it and make some notes about the concerns listed above.

StatsCan

Activity 2 – Comparing data at different scales

Using the information given at the site above, discuss the following question with a partner.

Based on our previous discussion, what are the main issues when we compare the data at 1:250000 to the data at 1:50000?

Each student will then post an entry in your blog giving an evaluation of the site as a source of data. Name this entry “Data Source evaluation”.

Activity 3 – Comment on Evaluation

You are to post a comment on at least two of your classmates’ postings on Data Source Evaluation.

Activity 4 – Exploring the National Topographic System (NTS) of Canada

Use this link to find basic information on the NTS.  How are the mapsheets organized?

Activity 5 – Further details on NTS data formats (Optional)

Download the Canvec Distribution Formats document (this may take a few minutes) and save it to your home drive (F:\).  The information found in Appendix A will be used to rename the digital files using ArcCatalog, at a later date (Data provided by this Provincial source generally have coded names).

Activity 6  – Further information on NTS data attributes (Optional)

Download the Canvec Feature Catalogue document (this may take a few minutes) and save it to your home drive (F:\).  This document gives details about the attributes associated with each feature dataset.  We will walk through parts of this document together.

Activity 7 – Retrieving NTS mapsheet information

The Natural Resources Canada website helps us to determine the NTS mapsheet number we may be interested in, by providing a query tool.  Use the Toggle NTS Grid button next to the map scale to see the NTS Sheet numbers

Use the clickable map and the name options to find the mapsheet on which Kamloops Lake sits.  The Mapsheet numbers are presented in a medium gray text e.g. 92l16.

Activity 8 – Determine the NTS mapsheets that cover a local area

Examine a map that shows the extent of the Town of Barriere (or a town of your choice within BC).

Use the ‘Clickable Map’ option to create a list of NTS sheets required to fully cover this geographic area.

Activity 9 – Recording NTS numbers

Provide the name of  the town you investigated and NTS number(s) of the mapsheets that contain its boundaries

Activity 10 – Exploring the BC  Geographic System

Use this link to look at the BCGS Map Numbering System

Activity 11 – Recording BCGS mapsheet numbers

Post the BCGS mapsheet number(s) that contain the boundaries of the town you investigated in Activity 8.  Use the tool provided at the site above