Introduction

The Role of Maps

Maps have played an important role in human activities for thousands of years. The world consists of things that are geographically (or spatially) related to each other. Although maps can be exacted as copies of the world, they are usually not. Maps are models that contain the representation of world things, but these representations do not need to be similar to what they represent, or even have the same spatial relationship. The real world is the domain of geographers and geography. Geographers live on the surface of a large, nearly oblate ellipsoid with terrain - that is, in three-dimensional space. A map is where cartographers live - it's small and flat. The process of representing things in the real world on this plane is mapping.

The golden age of maps and cartography corresponds to the era of exploration. Maps are the key to great wealth. The tools that propelled the last golden age were the compass, sextant, precise clock. Digital maps, geographic information systems (GIS) and location-based services represent the next golden age of maps and cartography. The tools that drive this era are computers, the Internet, and the Global Positioning System (GPS).

In the modern world, clear and powerful communication of information is essential for business, science and politics. Whether the information to be conveyed is demographic data, opinion poll results or environmental data, it is geographically distributed. Just as a chart presents digital information in an easy-to-understand way, a map can show the relationship between information and location more clearly than any table format, allowing users to view information based on their spatial orientation.

Although this distribution information is implicit in the digital table, it is difficult or impossible to see it without showing on the map. Historically, accurate maps are difficult to produce and maintain, these factors limit the effectiveness of paper maps without any competitive technology.

The roadmap provides a good example of a limited map. We all put them in our cars - they're always out of date. If they don't blink, they are hard to read, and the streets we are looking for can move at any time. If we don't want to see the street, but want to see the location of Chinese restaurants in the town, we have to buy different types of maps. In other words, maps are often dense, single-purpose documents that are used as archives of past locations.

Application of Digital Map

Digital maps ensure that graphics and images are rendered conveniently and effectively. Therefore, they can also dynamically display the current information in real time.

However, hard mapping has been (and remains) the collection and maintenance of basic information. In fact, the dynamic characteristics of digital maps aggravate the maintenance work, because the performance and data requirements are very high.

The development of digital maps is driven by the needs of industry (such as mining), natural resource managers and researchers, which is used as a management tool.

However, with the rise of the Internet and the commercialization of hardware, digital maps are everywhere - the weather maps shown in the morning weather reports, Driving instructions obtained from GPS-enabled car navigation systems, as well as Internet sites that provide street maps on demand. Today is just a few common digital map apps.

However, most of these applications are unable to meet the needs of mobile users. For example, a GPS-enabled car navigation system can determine your current location and tell you how to get to other places, but since it can only access on-board data (at best), Therefore, it is impossible to provide a service that requires real-time information. These services will include best routing with congestion avoidance and real-time location-based services (for example, the lowest fuel price within five miles).

However, applications with network awareness and intelligence are being developed (ie, they are wireless and GPS enabled). Some examples are management tools for GPS-enabled garbage collection, systems for providing driving instructions to emergency vehicles, and the system allows the shipper to locate the goods in transit. Mobile technologies such as WiFi, 2.5 and 3G cellular will bring new possibilities.

When wireless technology is everywhere and bandwidth is cheap, what is the killer application? Before the advent of the Internet, no one would predict the popularity and profitability of companies like Google - a directory of tens of millions of computers on the Internet that anyone can use for free. This particular application is the invention of two college students who has a good idea and an opportunity to get cheap technology. While I won't try to predict the content of the killer mobile app, the fact that it will become a mobile app indicates that the mapping feature will be a necessary aid.

The role of open source GIS

The problem is that if some smart college students want to integrate killer apps and get rich, the data and/or services needed to get into the game can cost thousands of dollars. Although proprietary technology is powerful, it is very expensive. Whether it's buying proprietary software directly, ordering spatial information or outsourcing the entire application, using commercial software to produce high-quality map applications is expensive. If you have a stable set of system requirements, some of the bank’s funds and the market opportunities that are right for you, proprietary options may be a good choice. Similarly, if you prefer to make development and maintenance a headache, or if you anticipate a large amount of iron for traffic, you may want to use a proprietary product.

However, if you enter the market tentatively, with a dynamic system requirement (or not at all); Maybe you are short of funding, or just trying to use the technology, you should investigate and understand MapServer, which is the subject of this tutorial. MapServer is a map rendering engine that can be run as a CGI script or as a standalone application in a web environment through APIs accessible from multiple programming languages. Refer to the instructions in the MapServer home page, "MapServer is an OpenSource development environment for building space-enabled Internet Web applications." With the help of the University of Minnesota, NASA and the Department of Natural Resources of Minnesota, MapServer is now available to nearly 20 developers from the world.

There are a number of reasons you might consider using MapServer: maybe your boss refuses to put the map into his pet project at the price of a commercial product and tells you to find something on the Internet, maybe you have a space that contains some spatial information. Dataset, you want to share it graphically online; Maybe you want to expand your own pet project, you feel that providing online maps can have a big impact, or you might just like a map, and think about making a beautiful map from a digital source to make you happy. But before you look at MapServer to see if it's what you need, you have to understand what it is. MapServer is a tool for presenting geographic data to the Web - it's not a full-featured GIS (although it can be used to build one).

MapServer application

This tutorial will introduce some open source GIS tools, but MapServer is used on the server side.

Below is a brief description of the three applications that can be developed using the MapServer API.(They can also be done via CGI, but the process is slow, cumbersome, and ugly.) By adding MySQL databases and programming languages like PHP, these applications can provide considerable functionality without the need for extensive development work, which is very difficult, and the spatial awareness part is done by MapServer. These are not particularly innovative, but they do prove the tasks that can be accomplished.

Real estate sales tool

You can create a space-aware directory by adding the latitude/longitude coordinates of each sales attribute to the MLS (multiple listing service) or similar service, provide features that users expect from a graphical interface (such as clicking and dragging a space to pop up queries and infoboxes when the mouse hovers over a hotspot).

Real-time tracking and tracking

By collecting GPS locations in real time and forwarding them back to the host via 2.5 and 3G cellular technology, MapServer can help you build customer-facing applications that show the actual location of the load in real time. The MySQL database is great for storing such data.

Real-time traffic advice and congestion avoidance

Collect traffic levels electronically or by manually entering GPS coordinates, street addresses or intersections - MapServer can display traffic levels in real time, provide them over the network, and suggest alternative routes.