<p>I am working on a shipping company and we have several applications to calculate the distance between two ports. My curiosity was triggered by the fact that, time by time I see a small change on the distance. For example, when the distance was 2000 miles it changed to 2003 miles.</p>

<p>I searched if there was any infrastructure changes on the port but my search came back negative.</p>

<p>How could this addition on miles be explained?</p>

CC BY-SA 3.0
2017-12-13T09:31:50.183Z
Does your software calculate the shortest distance independent of weather, sea state, and shipping route regulations - such as [Traffic Separation Schemes](https://en.wikipedia.org/wiki/Traffic_Separation_Scheme)?
daniel.heydebreck
CC BY-SA 3.0
2017-12-13T10:46:27.023Z
@daniel.neumann The software I am using is Netpas. As far as I understand it does not use any of the above. Only shipping route regulations should be used but why a route could be altered?
Emka
CC BY-SA 3.0
2017-12-13T12:14:15.747Z
It might be due to changes in the marine spatial planning in the coastal waters (wind turbine farms, military restricted areas, environmental protection areas, for other reasons *blocked* areas). Or are there maybe tides included in the routing software?
daniel.heydebreck
CC BY-SA 3.0
2017-12-13T12:17:07.380Z
According to the Netpas webpage it provides "*distance data with (S)ECA, Weather Forecast, Piracy Alert and many other powerful functions*". It sounds reasonable that you get slightly varying distances.
daniel.heydebreck
CC BY-SA 3.0
2017-12-13T12:24:37.990Z
@daniel.neumann Weather is not yet integrated, and SECA and piracy are parameters that remain constant to me.
Emka
CC BY-SA 3.0
2017-12-13T13:59:27.773Z
Are the map projections the same? Would tides come into play?
Inkenbrandt
CC BY-SA 3.0
2017-12-16T00:27:40.943Z
If TSSs are included, is it possible that the 2000nm was in one direction and the 2003 in the other? Using the other lane approaching a port could easily add a few miles.
Semidiurnal Simon
CC BY-SA 3.0
2017-12-18T07:49:18.067Z
@Inkenbrandt I am afraid I do not have any information about projections and tides are not considerate into the calculations.
Emka
CC BY-SA 3.0
2017-12-18T07:51:09.333Z
@Flyto I believe the same as you, but I cannot find any working example. Because whatever I have tried they return the same result regardless direction.
Emka
CC BY-SA 3.0
2018-01-18T02:16:33.770Z
Could be a setting to follow either great circle or thumb line (constant heading), which would be a bit longer.
Ben51
<oceanography>
Change on naval distances
Emka
# Change on naval distances

(Asked by: username_0 on 2017-12-13)

I am working on a shipping company and we have several applications to calculate the distance between two ports. My curiosity was triggered by the fact that, time by time I see a small change on the distance. For example, when the distance was 2000 miles it changed to 2003 miles.

I searched if there was any infrastructure changes on the port but my search came back negative.

How could this addition on miles be explained?

**Tags:** oceanography

> **Comments:**
> **username_1**: Does your software calculate the shortest distance independent of weather, sea state, and shipping route regulations - such as [Traffic Separation Schemes](https://en.wikipedia.org/wiki/Traffic_Separation_Scheme)?  
> **username_0**: @daniel.neumann The software I am using is Netpas. As far as I understand it does not use any of the above. Only shipping route regulations should be used but why a route could be altered?  
> **username_1**: It might be due to changes in the marine spatial planning in the coastal waters (wind turbine farms, military restricted areas, environmental protection areas, for other reasons *blocked* areas). Or are there maybe tides included in the routing software?  
> **username_1**: According to the Netpas webpage it provides "*distance data with (S)ECA, Weather Forecast, Piracy Alert and many other powerful functions*". It sounds reasonable that you get slightly varying distances.  
> **username_0**: @daniel.neumann Weather is not yet integrated, and SECA and piracy are parameters that remain constant to me.  
> **username_2**: Are the map projections the same? Would tides come into play?  
> **username_3**: If TSSs are included, is it possible that the 2000nm was in one direction and the 2003 in the other? Using the other lane approaching a port could easily add a few miles.  
> **username_0**: @username_2 I am afraid I do not have any information about projections and tides are not considerate into the calculations.  
> **username_0**: @Flyto I believe the same as you, but I cannot find any working example. Because whatever I have tried they return the same result regardless direction.  
> **username_4**: Could be a setting to follow either great circle or thumb line (constant heading), which would be a bit longer.  

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## 0 answers

