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Why must Chinese maps be obfuscated?
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Why must Chinese maps be obfuscated?
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According to this answer on Travel.SE, the Chinese National Bureau of Surveying and Mapping requires that published maps of China must include a certain deviation between the map and the real world.
In the comments, the answerer says that although the statute doesn't provide a reason, it is commonly believed to be for national security.
Have any Chinese officials or official documents provided a reason why maps must include this deviation?
china
asked 14 hours ago
indigochildindigochild
19.5k258140
add a comment |
According to this answer on Travel.SE, the Chinese National Bureau of Surveying and Mapping requires that published maps of China must include a certain deviation between the map and the real world.
In the comments, the answerer says that although the statute doesn't provide a reason, it is commonly believed to be for national security.
Have any Chinese officials or official documents provided a reason why maps must include this deviation?
china
asked 14 hours ago
indigochildindigochild
19.5k258140
add a comment |
According to this answer on Travel.SE, the Chinese National Bureau of Surveying and Mapping requires that published maps of China must include a certain deviation between the map and the real world.
In the comments, the answerer says that although the statute doesn't provide a reason, it is commonly believed to be for national security.
Have any Chinese officials or official documents provided a reason why maps must include this deviation?
china
asked 14 hours ago
indigochildindigochild
19.5k258140
According to this answer on Travel.SE, the Chinese National Bureau of Surveying and Mapping requires that published maps of China must include a certain deviation between the map and the real world.
In the comments, the answerer says that although the statute doesn't provide a reason, it is commonly believed to be for national security.
Have any Chinese officials or official documents provided a reason why maps must include this deviation?
china
china
asked 14 hours ago
indigochildindigochild
19.5k258140
asked 14 hours ago
indigochildindigochild
19.5k258140
asked 14 hours ago
indigochildindigochild
19.5k258140
asked 14 hours ago
indigochildindigochild
19.5k258140
asked 14 hours ago
indigochildindigochild
19.5k258140
19.5k258140
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
What the Law Says
After reading that statute, it turns out that it does not explicitly require that maps be obfuscated.
However, the law does require the usage of a certain datum. A datum is basically the mathematical model which describes the shape of the earth (see this question on GIS.SE for more detail). According to wikipedia, the agency responsible for implementing this model has created the GCJ-02 datum, which has a random disturbance - effectively slightly randomizing the location of objects on the map.
U.S. - Selective Availability
There are many unsourced claims online which say that this random disturbance is for security reasons. Although I couldn't locate an original source making this claim, there is precedent for it.
Prior to 2000, the United States Department of Defense required the usage of 'Selective Availability' (SA). SA was a technology built into the GPS system which introduced random errors. GPS.gov, the official U.S. source of information about GPS, describes it as:
Selective Availability (SA) is the deliberate introduction of error to the precise timekeeping of the GPS satellites, thereby reducing both positioning and timing accuracy for civilian users. It was designed to provide U.S. and Allied military forces with a navigational advantage in times of crisis or conflict.
(source: GPS.gov)
answered 8 hours ago
indigochildindigochild
19.5k258140
Not done yet, but this is what I have so far.
– indigochild
8 hours ago
1
Upvote, but the "error" in GCJ-02 datum does not seem to be random, i.e. it's security by obscurity (of the [conversion] algorithm). Quite a different thing.
– Fizz
34 mins ago
@Fizz "Random" has many meanings. An algorithm generating a predictable stream of numbers is still called a "random number generator". The output of an encryption algorithm is supposed to look random to the observer, etc.
– pipe
17 mins ago
add a comment |
Just to clarify, this isn't at all like the SA case where bits were unavailable unless you knew the key. The Chinese don't have their own GPS satellites (duh) setting these coordinates. What this GCJ-02 business is is a non-disclosed, but not-so-hard-to-reverse engineer conversion algorithm from other coordinates. The big picture looks like this:
That's the reverse-engineered conversion from the "bog standard" WGS-84, displayed as a vector field. As the blog from which I too that image says, the offsets are basically constant locally, but they vary across China.
It's speculated that Google doesn't do it except on their cn maps site in order to please Beijing. Other maps providers aren't so bothered.
answered 18 mins ago
FizzFizz
16.8k242108
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
What the Law Says
After reading that statute, it turns out that it does not explicitly require that maps be obfuscated.
However, the law does require the usage of a certain datum. A datum is basically the mathematical model which describes the shape of the earth (see this question on GIS.SE for more detail). According to wikipedia, the agency responsible for implementing this model has created the GCJ-02 datum, which has a random disturbance - effectively slightly randomizing the location of objects on the map.
U.S. - Selective Availability
There are many unsourced claims online which say that this random disturbance is for security reasons. Although I couldn't locate an original source making this claim, there is precedent for it.
Prior to 2000, the United States Department of Defense required the usage of 'Selective Availability' (SA). SA was a technology built into the GPS system which introduced random errors. GPS.gov, the official U.S. source of information about GPS, describes it as:
Selective Availability (SA) is the deliberate introduction of error to the precise timekeeping of the GPS satellites, thereby reducing both positioning and timing accuracy for civilian users. It was designed to provide U.S. and Allied military forces with a navigational advantage in times of crisis or conflict.
(source: GPS.gov)
answered 8 hours ago
indigochildindigochild
19.5k258140
Not done yet, but this is what I have so far.
– indigochild
8 hours ago
1
Upvote, but the "error" in GCJ-02 datum does not seem to be random, i.e. it's security by obscurity (of the [conversion] algorithm). Quite a different thing.
– Fizz
34 mins ago
@Fizz "Random" has many meanings. An algorithm generating a predictable stream of numbers is still called a "random number generator". The output of an encryption algorithm is supposed to look random to the observer, etc.
– pipe
17 mins ago
add a comment |
What the Law Says
After reading that statute, it turns out that it does not explicitly require that maps be obfuscated.
However, the law does require the usage of a certain datum. A datum is basically the mathematical model which describes the shape of the earth (see this question on GIS.SE for more detail). According to wikipedia, the agency responsible for implementing this model has created the GCJ-02 datum, which has a random disturbance - effectively slightly randomizing the location of objects on the map.
U.S. - Selective Availability
There are many unsourced claims online which say that this random disturbance is for security reasons. Although I couldn't locate an original source making this claim, there is precedent for it.
Prior to 2000, the United States Department of Defense required the usage of 'Selective Availability' (SA). SA was a technology built into the GPS system which introduced random errors. GPS.gov, the official U.S. source of information about GPS, describes it as:
Selective Availability (SA) is the deliberate introduction of error to the precise timekeeping of the GPS satellites, thereby reducing both positioning and timing accuracy for civilian users. It was designed to provide U.S. and Allied military forces with a navigational advantage in times of crisis or conflict.
(source: GPS.gov)
answered 8 hours ago
indigochildindigochild
19.5k258140
Not done yet, but this is what I have so far.
– indigochild
8 hours ago
1
Upvote, but the "error" in GCJ-02 datum does not seem to be random, i.e. it's security by obscurity (of the [conversion] algorithm). Quite a different thing.
– Fizz
34 mins ago
@Fizz "Random" has many meanings. An algorithm generating a predictable stream of numbers is still called a "random number generator". The output of an encryption algorithm is supposed to look random to the observer, etc.
– pipe
17 mins ago
add a comment |
What the Law Says
After reading that statute, it turns out that it does not explicitly require that maps be obfuscated.
However, the law does require the usage of a certain datum. A datum is basically the mathematical model which describes the shape of the earth (see this question on GIS.SE for more detail). According to wikipedia, the agency responsible for implementing this model has created the GCJ-02 datum, which has a random disturbance - effectively slightly randomizing the location of objects on the map.
U.S. - Selective Availability
There are many unsourced claims online which say that this random disturbance is for security reasons. Although I couldn't locate an original source making this claim, there is precedent for it.
Prior to 2000, the United States Department of Defense required the usage of 'Selective Availability' (SA). SA was a technology built into the GPS system which introduced random errors. GPS.gov, the official U.S. source of information about GPS, describes it as:
Selective Availability (SA) is the deliberate introduction of error to the precise timekeeping of the GPS satellites, thereby reducing both positioning and timing accuracy for civilian users. It was designed to provide U.S. and Allied military forces with a navigational advantage in times of crisis or conflict.
(source: GPS.gov)
answered 8 hours ago
indigochildindigochild
19.5k258140
What the Law Says
After reading that statute, it turns out that it does not explicitly require that maps be obfuscated.
However, the law does require the usage of a certain datum. A datum is basically the mathematical model which describes the shape of the earth (see this question on GIS.SE for more detail). According to wikipedia, the agency responsible for implementing this model has created the GCJ-02 datum, which has a random disturbance - effectively slightly randomizing the location of objects on the map.
U.S. - Selective Availability
There are many unsourced claims online which say that this random disturbance is for security reasons. Although I couldn't locate an original source making this claim, there is precedent for it.
Prior to 2000, the United States Department of Defense required the usage of 'Selective Availability' (SA). SA was a technology built into the GPS system which introduced random errors. GPS.gov, the official U.S. source of information about GPS, describes it as:
Selective Availability (SA) is the deliberate introduction of error to the precise timekeeping of the GPS satellites, thereby reducing both positioning and timing accuracy for civilian users. It was designed to provide U.S. and Allied military forces with a navigational advantage in times of crisis or conflict.
(source: GPS.gov)
answered 8 hours ago
indigochildindigochild
19.5k258140
edited 7 hours ago
answered 8 hours ago
indigochildindigochild
19.5k258140
answered 8 hours ago
indigochildindigochild
19.5k258140
answered 8 hours ago
indigochildindigochild
19.5k258140
19.5k258140
Not done yet, but this is what I have so far.
– indigochild
8 hours ago
1
Upvote, but the "error" in GCJ-02 datum does not seem to be random, i.e. it's security by obscurity (of the [conversion] algorithm). Quite a different thing.
– Fizz
34 mins ago
@Fizz "Random" has many meanings. An algorithm generating a predictable stream of numbers is still called a "random number generator". The output of an encryption algorithm is supposed to look random to the observer, etc.
– pipe
17 mins ago
add a comment |
Not done yet, but this is what I have so far.
– indigochild
8 hours ago
1
Upvote, but the "error" in GCJ-02 datum does not seem to be random, i.e. it's security by obscurity (of the [conversion] algorithm). Quite a different thing.
– Fizz
34 mins ago
@Fizz "Random" has many meanings. An algorithm generating a predictable stream of numbers is still called a "random number generator". The output of an encryption algorithm is supposed to look random to the observer, etc.
– pipe
17 mins ago
Not done yet, but this is what I have so far.
– indigochild
8 hours ago
Not done yet, but this is what I have so far.
– indigochild
8 hours ago
1
1
Upvote, but the "error" in GCJ-02 datum does not seem to be random, i.e. it's security by obscurity (of the [conversion] algorithm). Quite a different thing.
– Fizz
34 mins ago
Upvote, but the "error" in GCJ-02 datum does not seem to be random, i.e. it's security by obscurity (of the [conversion] algorithm). Quite a different thing.
– Fizz
34 mins ago
@Fizz "Random" has many meanings. An algorithm generating a predictable stream of numbers is still called a "random number generator". The output of an encryption algorithm is supposed to look random to the observer, etc.
– pipe
17 mins ago
@Fizz "Random" has many meanings. An algorithm generating a predictable stream of numbers is still called a "random number generator". The output of an encryption algorithm is supposed to look random to the observer, etc.
– pipe
17 mins ago
add a comment |
Just to clarify, this isn't at all like the SA case where bits were unavailable unless you knew the key. The Chinese don't have their own GPS satellites (duh) setting these coordinates. What this GCJ-02 business is is a non-disclosed, but not-so-hard-to-reverse engineer conversion algorithm from other coordinates. The big picture looks like this:
That's the reverse-engineered conversion from the "bog standard" WGS-84, displayed as a vector field. As the blog from which I too that image says, the offsets are basically constant locally, but they vary across China.
It's speculated that Google doesn't do it except on their cn maps site in order to please Beijing. Other maps providers aren't so bothered.
answered 18 mins ago
FizzFizz
16.8k242108
add a comment |
Just to clarify, this isn't at all like the SA case where bits were unavailable unless you knew the key. The Chinese don't have their own GPS satellites (duh) setting these coordinates. What this GCJ-02 business is is a non-disclosed, but not-so-hard-to-reverse engineer conversion algorithm from other coordinates. The big picture looks like this:
That's the reverse-engineered conversion from the "bog standard" WGS-84, displayed as a vector field. As the blog from which I too that image says, the offsets are basically constant locally, but they vary across China.
It's speculated that Google doesn't do it except on their cn maps site in order to please Beijing. Other maps providers aren't so bothered.
answered 18 mins ago
FizzFizz
16.8k242108
add a comment |
Just to clarify, this isn't at all like the SA case where bits were unavailable unless you knew the key. The Chinese don't have their own GPS satellites (duh) setting these coordinates. What this GCJ-02 business is is a non-disclosed, but not-so-hard-to-reverse engineer conversion algorithm from other coordinates. The big picture looks like this:
That's the reverse-engineered conversion from the "bog standard" WGS-84, displayed as a vector field. As the blog from which I too that image says, the offsets are basically constant locally, but they vary across China.
It's speculated that Google doesn't do it except on their cn maps site in order to please Beijing. Other maps providers aren't so bothered.
answered 18 mins ago
FizzFizz
16.8k242108
Just to clarify, this isn't at all like the SA case where bits were unavailable unless you knew the key. The Chinese don't have their own GPS satellites (duh) setting these coordinates. What this GCJ-02 business is is a non-disclosed, but not-so-hard-to-reverse engineer conversion algorithm from other coordinates. The big picture looks like this:
That's the reverse-engineered conversion from the "bog standard" WGS-84, displayed as a vector field. As the blog from which I too that image says, the offsets are basically constant locally, but they vary across China.
It's speculated that Google doesn't do it except on their cn maps site in order to please Beijing. Other maps providers aren't so bothered.
answered 18 mins ago
FizzFizz
16.8k242108
answered 18 mins ago
FizzFizz
16.8k242108
answered 18 mins ago
FizzFizz
16.8k242108
answered 18 mins ago
FizzFizz
16.8k242108
16.8k242108
add a comment |
add a comment |
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