The map is not difficult to draw, and Li Mu can draw it anytime and anywhere. Moreover, he can draw not only ordinary geographical contour maps, but also major mountain ranges and rivers, contour maps, and so on. Because when he was in junior high school, he was very interested in geography.

It is not difficult to draw, the difficulty lies in how to express the concept accurately and without being obtrusive. How to explain how such an accurate map was drawn.

Since he had the idea of drawing a map, Li Mu began to collect information. In order for the Tang people to accept the map he draws, he must first know how the Tang people drew the map.

Through Lu Wenfeng in Yubu Langzhong, Li Mu had a certain understanding of the mapping methods of the ancients.

The ancients drew maps, which is very different from Li Mu's previous life. In Li Mu's previous life, science and technology were already very developed, and drawing a map was very simple, and only a high-resolution satellite was needed to do it very accurately. Systems such as 'Beidou', 'GPS', and others consisting of dozens of satellites are able to pinpoint objects even within a meter of each other, not to mention geomorphological features.

But the ancients, without satellites, also had their own methods.

First, you need to select a coordinate system. What kind of coordinate system is suitable, in people's field of vision, there is nothing more than mountains and rivers. As a result, there is the "Classic of Mountains and Seas", with mountains and rivers as coordinates and rivers as the veins. Beginning from the mountain, ending from the sea, hence the name "Classic of Mountains and Seas", "Classic of Mountains and Seas" as an encyclopedia of the pre-Qin period, it records a large number of mountains, rivers and distances, how many miles apart the two mountains, there are general records. Although many people find it implausible that the "Classic of Mountains and Seas" is mixed with myths and legends, the narrative of geography in it is still somewhat credible due to the vision that people at that time could reach.

However, geography books such as "The Classic of Mountains and Seas" are, after all, very general, not precise at all, and not very practical. With the progress of human society, the requirements for maps have become more and more accurate. At this time, a new method of drawing was born.

From "coordinate system" to precise measurement, how to measure accurately? It is naturally not possible to rely on both legs, firstly, the area is thousands of miles, and you can't afford to walk at all. Furthermore, everyone's "steps" are of different lengths, and they are still not accurate. Therefore, since Qin Shi Huang unified weights and measures, the concept of 'li' was prescribed. At this time, a new method of measurement was born, using horse-drawn carts.

In ancient times, the map was also called "geographic", and this "map" refers to the car. This set of equipment is called "Jili Drum Car". The appearance of the drum cart in Jili in the Qin Dynasty was quite perfect by the time of the Han Dynasty, and its operation was so ingenious that in the Tang Dynasty, it was still the main method of drawing maps.

Prepare a horse-drawn carriage, place a drum on the carriage, a gong on the other, divided into two layers, two wooden people, the car is equipped with a compass, every time the car travels one mile, the wooden man will beat the drum, every ten miles, will strike the gong.

To draw a map and measure the distance, you only need to pull the "Jili drum car" to run all over the country, record the river channel, the edge of the region, and only need to record the mileage of the bend to draw the outer outline of the territory.

The data obtained from the drum car in the book is not the end. The important thing is to draw a graph, and anyone can do it by recording data, but the step of drawing a graph is not something that ordinary people can do. Because this involves a relatively deep knowledge for the ancients, the scale, which the ancients called "planning and drawing".

The first step is to draw squares of equal area on the drawing, and set a number of feet for each square, such as how many miles is equal to one foot. The diagram drawn in this way, in a limited and small range, is already very accurate. But it has a huge flaw, that is, the ancients did not know that the earth is a ball, so they did not have the concept of latitude and longitude. In a small area, such as a city, or even a small country during the Spring and Autumn Period and the Warring States Period, the map can be relatively accurate. But looking at the whole territory, by the middle of the place, can still ensure a certain accuracy, the closer to the two ends, because the earth is a ball, the curvature of the relationship, the more deviated.

The map drawn by Li Tai is this problem. What he drew was a map of the territory of the Tang Dynasty, which included all the current territories of the Tang Dynasty. Before this map, there had never been such a large map. The main local map used is a small area map within the scope of 'Fudao County'. That is, a relatively accurate map drawn by the drum car in the plan and the drum car in the book.

And Li Tai put these maps together and drew a map of the entire territory of the Tang Dynasty. He couldn't be wrong, but he didn't take into account the latitude and longitude, so that the map was inevitably skewed.

Of course, in Li Shimin's eyes, since he had never seen the accurate map that Li Mu had seen in his previous life, Li Tai's map was already breathtaking to him. But in Li Mu's eyes, Li Tai's map couldn't be more clumsy, and he couldn't stand it at all.

But if you want Li Tai to accept his map, the first thing to do is to make Li Tai accept the concept that the earth is round.

How to prove it? It's a problem!

……

"I think the earth under my feet is round."

When Li Mu said this, he felt full of doubts from everyone. It was the most straightforward way he could think of. Because he couldn't think of any explanation for the fact that the earth was round, and even in his previous life, when there were no satellites, there was a debate for thousands of years about whether the earth was round or flat or an arc plane. It wasn't until Magellan returned to square one in the Great Voyage that the world accepted the fact that the earth was round.

In the Tang Dynasty, sailing across the strait was a matter of life and death, and sailing around the world was impossible for Li Mu to do even if he had a system. So he just can't prove it, but he still has to say it, so he can only be like all the forerunners, you think I'm crazy, that's what I think, that's what I say!

Li Tai's eyes widened and said, "Big ...... Teacher, how can the earth be round? ”

"Hmm," Li Mu cleared his throat and said, "I can't say clearly, that's what I think." Li Mu gave an example of a bit of a scoundrel and said: "If it is not round, let me ask you, the rolling Yangtze River flows eastward, so why is the Yangtze River not exhausted, but has been flowing eastward for thousands of years?" If the ground is not round, then there must be a day when it will run out, and if it does not run out, it must be round, flowing from west to east, and then going around in a circle, and then returning to the source, so that we can explain why it has been flowing endlessly. ”

Li Tai's brain couldn't keep up with it, he felt as if something was wrong, but due to the limitations of the times, he didn't know what evaporation was, what condensation was, and what atmospheric circulation was, so he couldn't refute Li Mu's point of view, although he remained skeptical, he wisely didn't speak.

Changsun Chong and the others were watching from the side, and they couldn't find fault with it. They can't even draw a map, they're just laymen, how can they understand what it means? It's just to join in the fun, I just want to see what the map drawn by Li Mu looks like.

Li Mu knew that his statement was untenable, and he didn't give Li Tai more room to think, so he directly took out the map he drew overnight. A map of the territory of the Tang Dynasty is the same as the name of Li Tai's map, but he is drawn with a charcoal pen sharpened by animal charcoal, and there is a sense of sketching, which looks much more accurate than the map drawn by Li Tai with a fine brush.

This map was 'localized' by Li Mu based on the map he saw in his previous life. The place names and regional divisions were all redrawn by him with reference to the existing Datang divisions, which were very different from those in his previous geography class.

The map of his previous life and the division of the main provinces, in fact, traced history, were set during the Yuan Dynasty. Because the Yuan Dynasty was a foreign power, in order to avoid the local people from being too united, it forcibly separated the regions that originally belonged to the same clan, and there was no natural danger to defend, so that even if a place rebelled, it could not be held and it was convenient to maintain the rule. The geographical division of the Tang Dynasty was very different from this. If you take it out directly, Li Tai will be even more incomprehensible.

Although Li Tai is young, he is a master second to none in the world in terms of map attainments. The layman looks at the bustle, and the insider only looks at the doorway, and Li Tai knew that Li Mu's map was much more accurate than his map at first glance. Although he doesn't know what's good, he can still tell the difference between the good and the bad.

Li Mu took out another picture, which was a map of Chang'an City that he had drawn. The scale setting was used to draw the area occupied by the 108 squares of Chang'an City in detail. This map came earlier than the map just now, because this map was a construction drawing he drew when he decided to repair the Chang'an roadway, and he took it out at this time, just to give Li Tai a look.

"What do you think? Convincing? ”

"Obey it!" Li Tai nodded his head violently, touched the map, as if stroking the hand of his beloved woman, looked at Li Mu with blank eyes, and said, "Teacher, can you give this map to the apprentice, I want to take it back and study it well." ”

"It's okay to send you, but you have to remember one thing, and remember in the future, there are people outside the people, and there are mountains outside the mountains. Don't make something out, you feel invincible in the world, draw a broken map, and give you a bang. I'm so good, have I ever shown off? Man, keep a low profile, and when you want to show off in the future, think about it first, where I want to show off, is there a teacher who surpasses me, if the answer is no, then don't show off, so as not to make people laugh. ”

Li Mu glanced at Changsun Chong as he spoke, and said, "You too, remember?" When you want to show off in the future, think about it. ”

The eldest grandson hurriedly said: "Teacher, I don't have the heart to show off anymore, the longer I follow my teacher, the more I feel my shortcomings, where do I dare to show off?" ”

"It's good to understand." Li Mu pointed to the map and said to Li Tai: "Put it away, work harder if you have nothing to do, and make a career as soon as possible, so that my face will shine." I don't dare to admit that outsiders hear that you are my disciple, for fear of being ridiculed. ”

Li Taiwei responded, there was no way, Li Mu had already proved his strength with strong facts, and he had to be convinced if he was not convinced.

"There's one more thing." Li Mu suddenly spoke up and said, "Can't you lose weight?" You're only eleven years old after the New Year, and now you have to have 200 pounds, right? ”

"Master......" Li Tai said aggrievedly: "I, I'm only one hundred and seventy pounds now." ”

"Eleven-year-old one hundred and seventy pounds, are you still too little?" Li Mu said angrily: "Eldest Sun Chong, King Yue will be handed over to you, how you lose weight, you can train him." On the last Yuan Festival, I want to see him lose as much weight as you are now. ”

The eldest grandson Chong knows how he lost weight, Li Tai is Li Shimin's son after all, how dare he treat Li Tai like Li Mu treats him, why is it: "Teacher, King Yue's ......"

"In my place, you are senior brothers, senior brothers teach junior brothers, what else can't you do? Li Tai, do you think it can't be? ”

Li Tai hurriedly shook his head and said, "I didn't say anything, what the teacher said is what it is." The disciple has no complaints, he just wants to learn more skills. ”

"Hear that?" Li Mu waved his hand, and everyone retreated. Fang Yiai sent everyone to the door, and when he came back, he was stopped by Dugu Jiu. Fang Yiai looked at Dugu Jiu vigilantly, and said nervously: "What do you want to do, fight?" ”

"Yes and no. You go to a place with me. ”

"Where are you going?"

"You'll find out when you go."

Dugu Jiu was too lazy to talk nonsense, and walked straight out with his sword. Fang Yiai saw that he didn't ride a horse, so he didn't ride himself, and shouted into the study, telling Li Mu that he had gone out with Dugu Jiu, and then trotted behind Dugu Jiu, he couldn't work lightly, and he couldn't keep up with Dugu Jiu's footsteps.

The two of them came out of the back door of the phoenix, walked all the way east, and came to a clearing, the north of the clearing, not far from the racecourse. Fang Yiai has never been here, and he feels strange, but he doesn't dare to ask, seeing that there are many craftsmen working here, like building another high platform, he began to guess in his heart, what is this for?

This is that he doesn't have the habit of reading Datang Daily, if he had read it, he would have guessed that this was building a ring.

Dugu Jiu pointed to the ring and said, "Big brother has decided to hold a ring competition to select the first ranger of the Tang Dynasty......"

Fang Yiai hurriedly said: "I must participate, I have long wanted to be a ranger." But the first ranger of the Tang Dynasty, I don't have much confidence. ”

Under the mask, Dugu Jiu had to turn his eyes to the sky, he really couldn't figure it out, how could Fang Yiai have the confidence to say such a thing? Don't look at him as big and three thick, but in Dugu Jiu's eyes, Fang Yiai is also the color of the three moves, the first ranger in the world? The hundredth won't be his turn!

"This has nothing to do with you, this is what the eldest brother told me. I came to you to tell you another thing, the repair of the Chang'an laneway, you know? ”

"You know, what's wrong?"

"The roadway has been repaired, and someone needs to take care of it, what the eldest brother means is that he wants you to find some young masters to form a team, and in the future, they will be in charge of these things, and they will be under the jurisdiction of Jinyiwei of the Internal Affairs Bureau, called the 'Chengguan Brigade'."