An Introduction to GIS and WebMapping - Lecture Material - Completely GIS dan Remote Sensing tutorial - facegis.com
GIS and WebMapping

Before diving right into using this web mapping application, you may want to take a few minutes to familiarize yourself with some of the basic concepts behind Geographic Information Systems (GIS) and what they can do for you. This tutorial is intended for new users of this application who have not had much exposure to other GIS or web-based mapping systems. We will begin with an overall discussion of GIS technology and then focus on how to use one of the various CRD Web-based GIS products.

GIS Tutorial

“What is GIS?”

A Geographic Information System (GIS) is a computer system that stores, manages, maps and analyzes geographic data. Geographic data combines and links graphic representations of "features", or "events" found on the earth with corresponding tabular data, which is also called attribute data. The following example illustrates this concept with schools. Schools are represented here by single point locations. In a single record of information, each point has associated with it not only its exact location on the earth but also information about the school, such as its name, and the type of school it is.

Features or events can be things as diverse as light poles, rivers, accident locations, delivery routes, historic battlegrounds, or the distribution of malaria cases. The linking of geographic or spatial information, with more traditional types of information (like school name, phone number and number of students) is what makes a GIS unique and is the basis for all GIS functionality. Spatial information uses location, within a coordinate system, as its reference base. The most common representation of spatial information is a map on which the location of any point could be given using latitude and longitude, or local grid references.

In general, people use a GIS for four main purposes: data creation, data display, analysis, and output. You can display objects according to the data in your database which is a very powerful feature. GIS analysis tools allow you to do things like find out how far your best customers travel to visit your store, which land parcels are within a flood zone, and which soil type is best for growing a particular crop. Output options include cartographic-quality maps as well as reports, lists, and graphs.

“How is GIS data stored and used?”

A GIS stores information about the features and events in a collection of thematic "layers" or coverages as the following graphic illustrates. In fact, it is the most distinguishing feature of a GIS to find and display (map) the location of features or events. For example, a traditional computer system may store all information about schools. It will provide the user with a list of all the schools, possibly including addresses, but the user still doesn't know where exactly the schools are. The answer to such a simple questions as: "Are the schools evenly distributed across town?" is impossible to give with traditional computer systems. The following example will illustrate this simple functionality. It will show how locational information alone, without any further analysis, is very useful.

A maintenance crew for light poles is scheduled to replace all light poles in town that are over 50 years old. The crew has a database about the light poles that includes the date of installation. In a traditional database, they could query the database and get a list of the light poles that are over 50 years old. But, where are they? The GIS combines the location and the age information and immediately displays a map that shows the location of all light poles that are over 50 years old. It is much easier now to schedule work for the crew in an efficient manner, because they can quickly develop a route through town to replace the light poles.

“What does GIS data look like?”

GIS data is comprised of graphical features (lines, points and polygons for example) and a table associated with each feature. The graphical features show a location on a map. Each individual feature has a record associated with it.

In this example, each of the parks on the map has information associated with it, which appears in a linked table. The information (attributes) about the highlighted park such as Name, Jurisdiction, Park Type, Size, etc. are also highlighted in the tabular database.

Using a query to pick out particular geographic features based on a set of criteria would be considered geographic analysis. This example illustrates this concept. We can use the GIS to show us all the parks that are managed by the District of Saanich and that are greater than 50 Ha in area.

“What can a GIS do?”

A GIS offers a wide variety of tools to manipulate, query, analyze and visualize geographic data. The type of analytical tools that GIS offers are often referred to as geographic or spatial analysis. The location of a feature or event is what drives the analysis. Before GIS was available, geographic analysis was very cumbersome, sometimes impossible, and often simply not done. However, in today's environment, critical questions are often asked that require this very capability. For example:

"What is the fastest route to the emergency?"

"Which commercial district in town generated the most sales tax revenues?"

"Which properties in town are between 20 and 30 acres, with zoning that allows for a recycling facility?"

"Which homes are within 500 feet of the floodplain?"  or extending our Parks example;

“Which parks are managed by the District of Saanich, are greater than 50 Ha in size, have Garry Oak Ecosystems represented within them and are within 15 km of the ocean?"

As you can see, GIS can answer a wide variety of spatially related and often very complex questions about he features that have been mapped, be they man-made or natural.

“Who uses GIS?”

GIS is used by many industries, including utilities, commercial businesses, law enforcement, transportation, health care, agriculture, and all levels of government. Water supply companies use GIS as a spatial database of pipes and manholes; local governments can use GIS to manage and update property boundaries, emergency operations and environmental resources. GIS may also be used to map out the provision of services, such as health care and primary education, taking into account population distribution and access to facilities. Increasingly, GIS is being used to assist businesses in identifying their potential markets and help determine the best location for a new business based on factors such as income statistics, competitor locations and ease of access. Industry is using GIS for things like natural resource management, land use planning, demographic research, emergency vehicle dispatch, fleet management, environmental assessment and planning, and much more. The number of GIS applications on the Internet is also growing rapidly.

Using the CRD’s Web-Based GIS Sites

The CRD maintains and hosts a number of different web-based mapping applications. The Natural Areas Atlas and Harbours Atlas are both available to the general public via the main CRD web page. A separate application called intraMap is also available to CRD Staff and provides detailed property information. You can think of these mapping websites as ‘lite’ versions of a full-blown GIS. They will provide you with a subset of the viewing, querying and map-making functionality that a professional, desktop GIS software package would provide.

Interactive Demo

If you have never used a GIS before or are new to web-based mapping, you may be interested in a quick, animated demo of how people use such sites. This Interactive Demo is geared specifically for The Natural Areas Atlas but it will give you an initial overview of some of the things you can do with any one of these sites hosted by the CRD.

Understanding the Map Viewer

The purpose of this section of the tutorial is to give detailed instructions on how to use any one of the various CRD Web-based GIS products. All of these sites share the same framework and many of the same layers and as a result, they look very similar. Let’s begin by examining the main window that appears when we launch the Natural Areas Atlas and describe the various ‘panes’ that it is comprised of.

The Tool Bar

TheTool Bar houses a wide variety of icons which allow the user to interact with the map and data. These icons are grouped into the five different categories outlined here. Specific details about all of the tools in each of the categories (and what they do) are provided in the help system.

Navigation tools are used to move around on the map.

Selection tools are used to highlight or select certain features based on their spatial positions. Only features in the active layer can be selected by one of the selection tools.

Information tools are used to find out more details about features seen on the map.

Markup tools are used to place annotation or graphics on the map. Be aware that you cannot save your markups, and they will not appear if you refresh the map or finish your session.

Other is a catch-all category for the refresh, print, feedback, help and exit tools.

The Map Window

This is the main area of the webpage and takes up the most room on the screen. This is by design as this is the ‘pane’ where users look at and interact with the map – the most important part of a mapping application after all!

The Scale Box

This small read out in the bottom, left-hand corner of the window shows the approximate scale that the map is currently displayed at. Users should note that the scale shown in this box is relative and intended for on screen use only. The accuracy of this number will vary with the size of your display and your resolution settings. For example, scale error will be most pronounced if you are using a large monitor, with a very low resolution setting or conversely, a very small monitor with a high resolution setting. The generic setting at which the displayed scale is most accurate would be a 17" monitor running at a resolution of 800x600 or 1024x768. The scale box is also interactive and the scale of the map can be manually changed by the user by highlighting and then typing new numbers into this box.

This is likely as good a spot as any to discuss the concept of Scale Dependency. Each of the layers shown in the Natural Areas Atlas has what are called scale dependencies set for it. This means that different layers will turn themselves on and off as the user zooms in and out. For example, Major Roads are visible at scales greater than 1:250,000 while all other roads do not turn on until you have zoomed into 1:20,000. This results in more information becoming available, the further in you zoom. This is necessary because if all the layers were shown all the time, it would make for a very disorienting and cluttered map.

The Status Area

This area found just below the main Map Window tells the user what the Active Layer and Active Tools currently are. This is important information and experienced users double check their status here regularly. A common mistake when using the identify tool to find out more information about a feature is to have the wrong layer selected as the active layer. By checking the Status Area, users can confirm both the Active Tool and Active Layer, thereby avoiding error messages.

Cursor Coordinates

This area, located in the bottom, right corner of the window, gives the coordinates of the cursor on the map. These coordinates are given in metres Easting and metres Northing using the Universal Transverse Mercator or UTM (Zone 10) system. These coordinates can be useful for identifying the exact location of an object or area of interest and can then be entered into a GPS unit for example.

The Layer Control and Information Panel

This area or ‘pane’ of the window has a somewhat cumbersome name because it does so many different things. In order to free up as much space as possible for the map window, we have used this area for four different tasks: the Layers, Legend, Bookmarks and Metadata tabs.

This is the list of all the different thematic ‘layers’ available for viewing. The layers are organized into logical groupings within folders which look very similar to the Windows Explorer environment. Click on the folder (1) to show or hide its contents

This is also where the user controls which layers are ‘turned on’ or ‘turned off’ and therefore visible. Layers are turned on by clicking in the check box (2) beside them.

Clicking on the green square (3) beside the folder will turn all layers in that folder on and conversely, clicking on the white box (4) beside that will turn all layers in that folder off.

When the checkbox and the ‘Information Icon’ for a layer appear grey (5), this means that layer is not visible at the current scale, because of the Scale Dependencies set for that layer. If this is the case, a red asterisk (6) will also appear to the right of the layer name. By hovering the cursor over this star, the user can see the minimum scale at which this layer is visible and by clicking on the star, the map is zoomed into that scale.

The Active Layer is also controlled here and is indicated by the dark blue ‘Information Icon’ (7) beside the layer. The active layer is the one that you want to find something out about. For example, if you want to find out what the name of a Park is or how large a bird sanctuary is, you will have to make the appropriate 'layer' active. The active layer is also indicated at the bottom of the window, beside the scale box.

Finally, at the bottom of the layer list, users can select from one of two options with respect to how the map reloads after they have made a change. By clicking the “Automatically reload map” box, the user indicates that they would like the map window to be refreshed after every modification such as a layer being turned on or off. Conversely, if the “Automatically reload map” box is unchecked, a “Reload Map” button appears and allows the user to make any number of layer changes before manually telling the map to redraw. This can sometimes be the faster option if there are many changes to be made, instead of waiting for the map to redraw after every small change.

The notes section found below the layer list can act as an excellent quick reference when using the layer list. It gives descriptions of what all the different symbols mean and pointers on how to get the most out of the application.

The Legend Tab

According to cartographic standards, all maps must have a legend. This is a key or reference area which shows what all of the different symbols on the map represent. The legend on this web-mapping application is intelligent in that it only shows the symbols for those features or layers which are currently turned on.

There are three different types of symbols used in most GIS applications and all can be seen here:

Polygons (1) are used to show areas or shapes such as parks.

Lines (2) are used to represent linear features such as roads or trails.

Points (3) are used for features or objects with a distinct location, such as the end of a discharge pipe.

The Bookmarks Tab

The third tab in the Layer Control and Information Panel is the Bookmarks List. This is a list (1) of predefined map extents which allow the user to click one button and zoom directly to a certain area. At present, there is a spatial bookmark for each of the thirteen Member Municipalities and two Electoral Areas within the CRD as well as for a number of the different Gulf Islands.

At the bottom of the Bookmarks List is a section for Personal Bookmarks (2). This allows users to ‘save’ their frequently used maps for future use. For example, if a user always zooms into the same area on the map and always turns on the same layers, they may want to save this map as a Personal Bookmark to save time during subsequent visits to the website. As implied, the Personal Bookmark saves not only the spatial extent of the map that is currently shown on the screen but it also remembers which layers are visible for the next time.

A new Personal Bookmark (3) is simply created by finalizing the scale, area and themes that you want to preserve in the map window and then pressing the ‘Bookmark this Map’ button. You will then be prompted to name your Personal Bookmark.

To remove a Personal Bookmark simply press the red X (4) beside that bookmark in the list.

The Metadata Tab

The last tab in the Layer Control and Information Panel is the Metadata Tab. This is where users go to find out more information about the map layers that they are looking at. As the top of the tab explains, Metadata is data about data. Metadata for the Parks layer for example would give: an overall description of the layer (Federal, Provincial, Regional, and Municipal Parks in the CRD); the original data source (Environmental Programs Department at the CRD); the projection and datum of the file (UTM NAD83); the accuracy of the file (+/- 1m) as well as when the file was last updated (July, 2002). Links to other sites where more information may exist are often also given. Metadata exists for all of the layers shown in the different web mapping applications.

Source: http://207.34.170.105/help/tutorial.htm