• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.1
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• pp.287-295
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• 2013

This paper developed advanced gravity model for higher estimation accuracy, that deals with residuals. Previously studied paper using gravity model's residual, residual calculated that observed O-D value minus derived O-D value from gravity model, and this residual added to the target year's estimated value from gravity model. In this paper, residuals calculated on gravity model parameter estimation process, and this residual is revealed the same value that observed O-D value devided by derived O-D value from gravity model. And case study resulted that developed new gravity model that applied accordance rate of observed O-D value and derived O-D value from gravity model has higher estimation accuracy than other gravity models as basic gravity model and residual plused gravity model.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3D
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• pp.417-424
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• 2006

To get more accurate trip distribution estimation results, this study developed an improved gravity model. Using three different year's O-D table resulted from person trip survey, this study analyzed correlative between basic year's residuals and target year's residuals by gravity model. And resulted that the two have linear correlation. From this, improved gravity model was developed as adding basic year's residual to present gravity model. Developed gravity model was compared to present gravity model by estimation accuracy, and revealed that distributed trips from improved gravity model was more closer to real O-D than distributed trips from present gravity model.

• Journal of Korean Society of Transportation
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• v.31 no.2
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• pp.60-68
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• 2013

This study developed plural gravity models and their application method in order to increase the accuracy of trip distribution estimation. The developed method initially involves utilizing the coefficient of determination ($R^2$) to set the target level. Afterwards, the gravity model is created, and if the gravity model's coefficient of determination is satisfactory in regards to the target level, the model creation is complete and future trip distribution estimation is calculated. If the coefficient of determination is not on par with the target level, the zone pair with the largest standardized residual is removed from the model until the target level is obtained. In respect to the model, the removed zone pairs are divided into positive(+) and negative(-) sides. In each of these sides, gravity models are made until the target level is reached. If there are no more zone pairs to remove, the model making process concludes, and future trip distribution estimation is calculated. The newly developed plural gravity model and application method was adopted for 42 zone pairs as a case study. The existing method of utilizing only one gravity model exhibited a coefficient of determination value ($R^2$) of 51.3%, however, the newly developed method produced three gravity models, and exhibited a coefficient of determination value ($R^2$) of over 90%. Also, the accuracy of the future trip distribution estimation was found to be higher than the existing method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5D
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• pp.763-769
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• 2006

Gravity Model estimates target year's distributed trips using three variables like as origin zone's trip production, destination zone's trip attraction and traffic impedance between origin zone centroid and destination zone centroid. Estimating inner zone trip by gravity model is impossible because traffic impedance of inner zone has "0" value. So till today, for estimating inner zone trips, other methods like growth factor model are used. This study proposed inner zone trip estimation method that calculates inner zone's traffic impedance using established gravity model and estimates inner zone trips by putting calculated traffic impedance into the gravity model. 1988 year's surveyed O-D as basic year's O-D, proposed method's and existing methods(growth factor method and regression model)'s estimated results of 1992 year's and 2004 year's were compared with each year's real O-D by $x^2$, RMSE, Correlation coefficient. And resulted that the proposed method is superior than other existing methods.

• Journal of the Korean Data and Information Science Society
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• v.12 no.2
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• pp.103-111
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• 2001

Now a day, overseas tour which is due to economic development grows very much. In this situation, a forecast of overseas tour is required to establish tourism policy for tourism marketing. In this paper, we compare regression model and gravity model for a forecast of overseas tour. Using gravity model, this study also suggests an attraction which is suitable to our situation, and suggested attraction is compared and analyzed with another.

• International Area Studies Review
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• v.16 no.1
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• pp.243-274
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• 2012

This research analyzes the determinants of Korea's trade using the Gravity model, Chow test and panel data anaysis. According to the pooled panel OLS analysis using the gravity model and Chow-test, Korea's trade patterns before and after the 2008 financial crisis are heterogeneous. Variables of basic gravity model, GDP per capita, distance, and population, identically showed positive and significant correlation with trade volume before and after financial crisis, but also equally showed the decrease in absolute value of coefficient. On the other hands, Overseas Direct Investments(ODI) variable showed the increase in absolute value of coefficient. But TCI was no longer significant. This research is significant in that it is able to show the strategy for the long term growth in Korea's volume of international trade through econometric analysis based on data of 55 trading partner of Korea.

• Journal of Korean Society of Transportation
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• v.1 no.1
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• pp.43-47
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• 1983

Within the conventional transportation planning process, "trip distribution" has a significant role to play. The most widely applied trip distribution model is the gravity model, for which Wilson provided the theoretical basis in 1967. The concept of the gravity model, however, still remains ambiguous if we analyze the "trip distribution" with a disaggregate data set. Thus, this paper hypothesizes that the gravity technique is still valid even with the disaggregate data set, by proving that the estimated coefficients of the gravity model, which is derived under the principle of entropy maximization, are identical with those of the multinomial logit model, which is derived under the principle of individual utility maximization.tility maximization.

• Journal of Korea Port Economic Association
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• v.30 no.2
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• pp.133-143
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• 2014

The paper uses a panel gravity model to analyse the determinants of export via Gwangyang port for the period from 2000-2012. The gravity model includes export via Gwangyang port, GDP and population of trading partners, the distances between Korea and its partners, and Korea-ASEAN FTA dummy. Hausman test shows up which one is exactly appropriate between random effect estimation and fixed effect estimation to use panel dataset. It depends on whether or not existence or nonexistence of the correlation between unobserved omitted factors and variables. Fixed effect estimation is suitable for this paper by the rejection of null hypothesis. An Empirical analysis of this paper shows GDP influences positive effects and distance influences negative effects to Gwangyang port trading partners. In addition, the results strongly supported the effects of Korea-ASEAN FTA on the growth of Gwangyang port export.

• The Journal of the Korea Contents Association
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• v.8 no.9
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• pp.274-280
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• 2008

The new high order Earth's gravity Model(EGM2008) are expected to improve the application about the Earth's global gravity field. The objectives of this research are to present characteristics on the geoid heights of provinces in South KOREA which calculated from the height anomalies by Earth Gravity Models. For this, seven EGMs (EGM2008<2,190>, EGM2008<360>, EGM96, EIGEN-GL04C, EIGEN-CG03C, EIGEN-GL04S1, and ITG-Grace02S) selected. Geoid heights of fifty BM check points by GPS/levelling are compared with those by NORI-05 model and seven EGMs. And also, geoid heights of 30"$\times$30" grid points in land(sixes blocks ; $1^{\circ}\times1^{\circ}$ sampled) and sea (four blocks ; $1^{\circ}\times1^{\circ}$ sampled) areas of South KOREA by EGM2008 are compared with those by NORI-05 and six EGMs. The results show that geoid heights obtained from EGM2008(2,190) of NGA displayed the nearest results to those by GPS/levelling.

• Journal of Korean Society of Transportation
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• v.29 no.2
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• pp.81-89
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• 2011

Trip distribution is the second step of the conventional travel demand estimation process, which connects trips between origin and destination, while transport mode choice is the third step of the process, which chooses transport mode among several modes serving for each origin-destination pair. Although these two steps have closely connected, they have been estimated independently each other in the estimation procedure. This paper presents an integrated model combining trip distribution and transport mode choice, and also presents its solution algorithm. The model integrates gravity model adopted for the trip distribution process with logit model employed for the mode choice process. The model would be expected to cope with the inconsistency issue existing in the conventional travel demand estimation procedure. This paper also presents an equilibrium condition, sensitivity of the model, and compares them with those of existing models.