Archive for October, 2009
Please take a few moments to participate in our poll concerning your current and future plans regarding your development platform for web mapping applications.Read Full Post | Make a Comment ( 2 so far )
Google Maps provides a web mapping application wherein maps are produced in advance and served as a set of small tiles for assembly into one big image in the browser. The advantage of this approach is consistency of appearance and graphical quality of the map and, probably more important, enormous scalability that can be achieved. There is no need for server side processing to generate maps and individual map tiles are much smaller than the whole map presented at the user end, so they are able to be delivered and displayed much faster. The trade off is a big effort up front to generate nice looking maps and the need to fix zoom levels rather than allowing a continuous zoom, as is the case with older web mapping technologies. The approach has been copied by other online map technology providers. But what approach should you take if you’d like to present your own custom data on top of a Google Maps base layer without using markers, polylines, or polygons? Perhaps you have a large dataset stored in a shapefile and you’d simply like to convert this data to a format suitable for display in Google Maps. In this case it would make sense to pre-create custom map tiles of your data at various zoom levels and have them available for display.
Custom Tile Overlays
Custom tile overlays are custom data that sit on top of an existing Google base map. They are essentially a snapshot of your data at a particular time. The data is cut into a pyramid of static tiles that correspond to each zoom level. Typically you would use some type of tool to cut the data into static tile images. In the figure below you see an example of a custom tile overlay showing thematically mapped parcel data on top of a Google base map.
So what is the point of creating a custom tile overlay? Why not simply add your custom data as markers, polylines or polygons? The short answer is that when you are dealing with large custom datasets the performance of your application can suffer a great deal when you attempt to plot this data as markers, polylines, or polygons. Since custom tile overlays are pre-built static tile images the performance is greatly improved. Data does not have to be created dynamically each time the map is drawn. The downside to this is that your users don’t have as much flexibility in terms of obtaining additional information about your custom data. You can’t click on your custom tiles to obtain additional information like you can when you display InfoWindows when markers are clicked.
When it comes to building custom map tiles with the Google Maps API you essentially have two options: GTileOverlay and a custom GMapType. GTileOverlay is simpler to use than GMapType although its use is more limited. However, in most cases GTileOverlay will suffice.
GTileOverlay is used when you want your data to overlay an existing Google Maps base map. In most cases you will want to use one of several tools available for creating the map tiles that will need to be displayed at each zoom level. GTileOverlay requires three abstract methods including getTileUrl(), isPng(), and getOpacity().
There are many tools available for turning you data into a custom map tile. Today we will review GMapCreator. GMapCreator, has a graphical user interface and uses shapefiles or CSV files as data sources. We’ll take a look at some of the additional tools you can use to create custom map tiles in future posts.
GMapCreator is a freeware application designed to make thematic mapping using Google Maps simpler. The application takes a shapefile containing geographic areas linked with attributes and automatically generates a working Google Maps website from the data. It does this by pre-creating all the necessary files and saving them into a directory. Publishing the map on the web is then just a matter of copying files onto a web server, allowing Google Maps to be used with the majority of ISPs.
GMapCreator can be downloaded from the UCL Centre for Advanced Spatial Analysis. You do need to create an account to download the software.
Your shapefile data source is loaded into the application and displayed inside the map preview area. As seen below.
The data must have an associated .prj file that defines the projection of the data. This is necessary because GMapCreator automatically reprojects the data to fit with the Google Maps projection. Using GMapCreator you can define the output symbology for thematic, geographic extent, and maximum zoom levels.
Tiles are generated by GMapCreator based on the Maximum Zoom Level you select from the tool interface as seen below. The zoom level corresponds to the zoom levels available in Google Maps. Here we have set the maximum zoom level to a value of ‘14’. GMapCreator specifies how many tiles will be created at each zoom level. In this case the tile count is 1,173. You can obviously go above this value, but there is an exponential jump in the number of tiles generated by each increase in value of the zoom level. For example, if I move the maximum zoom level to a value of 16 the tile count jumps to 17,224 (at maximum zoom level of 18 it jumps to 267,496) so you have to consider the tradeoffs between the level of detail you need for your application and the time and disk space necessary for generating a large number of tiles. The number of tiles can exceed 1 million at the highest zoom levels.
Thematic mapping with GMapCreator is performed by clicking the ‘Cols’ button which displays the Colour Thresholds dialog. Values are applied against the attribute field selected in the drop-down box. You can also give each color value a description.
Once you have defined the output symbology and the maximum zoom level GMapCreator creates a directory of image files which serve as tiles along with an HTML template for displaying the data. As mentioned above please note that the number of tiles can be very large depending upon the maximum zoom level you have selected.
GMapCreator also creates an HTML template file for displaying the data. You will likely want to customize the template file with your own logos and text since by default is includes information for the UCL Centre for Advanced Spatial Analysis (CASA) as seen in the figure below.
To move the output of this tool to a production web server you need only move the HTML template file along with the directory containing the tiles. GMapCreator is an efficient, easy to use tool for creating custom tile overlays for your Google Maps application.
For more information on the Google Maps API please consider our e-learning courses including Introduction to the Google Maps API, Advanced Google Maps API Programming and the Google Maps Developer Bundle.
GeoSpatial Training Services would like to announce the availability of a new Internet based, instructor led course. Working with Geodatabases and Linear Referencing, taught by John Schaeffer of Juniper GIS, is designed to teach students all the fundamentals of the Geodatabase; creating and managing the geodatabase, using domains, subtypes and topology to better manage your data, using images with the geodatabase, and using specialized editing tools to correct and clean data, and creating routes.
Students will learn how to use Geodatabases by working through two realistic projects. The first project is preparing data for a burn plan on the Florida Panther Refuge; the second is working with stream data from the Wenatchee National Forest to analyze fish populations.
December 7th – 18th, 2009.
This course assumes you are comfortable with using ArcGIS 9.x for general GIS tasks and that you have had some editing experience. The course is written for ArcGIS 9.3.1, but will work with 9.2 and 9.3, though the dialog boxes might be slightly different.
The course is divided into three sections.
In the first section we will look at the basics of creating and managing a Geodatabase, and then converting data to the geodatabase format.
In the second section, we’ll show you how to use the geodatabase to validate or check you data for attribute and spatial errors, how to make data entry easier, and how to edit with Geodatabase Topology.
In the third section, we’ll work with Routes and Linear Referencing. Routes let you attach multiple data tables to linear features for analysis and mapping. The easiest way to think about routes is the milepost numbers you see as you drive down roads. Once you have established a route with “mileposts” you can then link this to multiple data sources. In the last module, we’ll show you a sample extension that will make it easier to manage and create reports on your geodatabase.
Section 1: Geodatabase Basics
Module 1: Geodatabase Concepts and Basics
Module 2: Converting Data to the Geodatabase Format
Module 3: Working with Rasters in the Personal Geodatabase
Section 2: Validating Data
Module 4: Validating Attributes – Subtypes, Domains, Relationship Classes
Module 5: Validating Features – Topology in the Geodatabase
Module 6: Editing Topology
Section 3: Linear Referencing
Module 7: Understanding Linear Referencing
Module 8: Editing and Using Routes for Analysis
Module 9: The Geodatabase Designer
GISCI Education Credit: 16 Hours
$500 if you register by October 31st. $567 thereafter.
You may also register by downloading the registration form and sending back to use via one of the methods listed on the registration document.
For more information please contact us at sales at geospatialtraining.com or 210-260-4992.
Recently Google announced their Base Map Partner Program for “authoritative” organizations to share their vector data sources as part of the improvement process for base maps in Google Maps, Google Earth, and Google Maps for Mobile.
Currently Google is accepting the following data sets:
- Parks and Protected Areas
- Points of Interest (hospitals, tourist attractions, government buildings)
- New Developments and Construction (residential, commercial)
- Road Networks
- Geocoded Addresses
- Parcel Boundaries
- Bicycle and Pedestrian Paths and Road Facilities
The USGS and USDA Forest Service have already provided improved park and water body data and obviously a number of unknown providers have supplied parcel data. The addition of parcel data to Google Maps has initiated a very interesting post and conversation regarding the source(s), accuracy, and legality of this data.
I should also mention that Google will no longer use TeleAtlas map data for the U.S. and will instead use its own data sources.Read Full Post | Make a Comment ( 1 so far )
The challenging economic climate that we are currently experiencing has prompted many organizations to cut training and travel budgets. However, you and other members of your organization still need to acquire the skills necessary to perform at a high level and implement various initiatives. In short, you need more “financially friendly” training options.
Over the coming months we will be offering various promotions designed to save you money AND allow you to acquire the skills you need to perform your current job responsibilities or perhaps take on a new project that requires some additional expertise.
GeoSpatial Training Services was founded on the premise that high quality GIS training should be affordable, self-paced, and not require travel to a distant training center. We have worked diligently over the past 5 years to make this a reality. Today we offer several dozen classes in various formats, all designed with our initial premise in mind.
Today we are announcing the following programs designed to “Save the Pig!”
Pay What You Can!
The October 5th – November 13th session begins soon. We’re still looking to fill up the last half dozen seats for this course. Many of you have expressed an interest in the course, but don’t currently have the funds to register. Our solution? Make an offer! Tell us what you can pay for the course and if it’s reasonable we’ll accept and get you registered. We can even accept multiple payments. Send offer to eric at geospatialtraining.com
Save the Pig Subscription – Silver Level
With our lowest level “Save the Pig Subscription” you don’t have to break the piggy bank to obtain GIS training. What is it? This annual subscription entitles you to download a total of 13 e-learning courses from Geospatial Training Services. The first month you download 2 courses of your choice and then each month thereafter you can select an additional e-delivery course. See below for applicable courses. In all cases, courses are available through e-delivery.
Our highest level “Save the Pig Subscription”. What is it? This annual subscription entitled you to download an unlimited number of our our e-learning courses. See below for applicable courses. In all cases, courses are fulfilled through e-delivery.
Some additional information on our subscriptions
- These are annual subscriptions. At the end of one year you will have the option to renew for an additional year.
- All courses fulfilled through e-delivery. This means you will receive an email containing a download link to the course. You then download the course and install it on your computer.
- After registering for a subscription, course requests should be sent to
- These are individual accounts and should not be shared by the entire organization
- The Silver Level subscription entitles you to 2 downloads the first month + 1 additional download each month thereafter for the year.
- The Gold Level subscription is unlimited. You can request as many courses as you’d like whenever you’d like.
- This includes any new courses that are released during the coming year.
Courses included in the subscription accounts are listed below.
- Arc2Earth for ArcGIS Users
- ArcGIS Desktop 101
- Integrating ArcGIS Desktop and Google Earth
- Mastering Python for Geoprocessing in ArcGIS
- Programming ArcObjects with .NET (Courseware)
- Programming ArcObjects with VBA
- Advanced Google Maps API Programming
- Building Rich Google Maps Interfaces with Dojo
- Creating Mapplets with Google Gadgets
- Debugging Google Maps Applications with Firefox and Firebug
- Introduction to the Google Maps API
- Building Web Based Google Earth Applications
- Dynamic Google Earth Applications
- Mastering KML for Google Earth
- Integrating GPS Data with GIS
- Introduction to GPS Technology
- Adding Digital Photos to GIS
- Working with Coordinate Systems in GIS & GPS
- GPS Mapping with ArcPad
- GPS Mapping with Trimble’s TerraSync and Pathfinder Office
- Future Courses (Geodatabase Fundamentals, Spatial Analyst, Bing Maps API, others)
We will be announcing additional cost saving initiatives over the next month so stay tuned for more information and please feel free to pass this along to others that feel would benefit from any of our programs.
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