Allocation of risk factors for geodetic tasks in construction schedules


 Road construction projects are characterized by multitasking and the influence of the correct implementation of one task on another. In the subject literature, we can encounter the analysis of risk factors throughout the project, and yet, we rarely find the distinction and characteristics of the impact of risk factors resulting from the implementation of planning and measurement tasks, the correctness and timeliness that have a huge impact on the performance of subsequent tasks, and the success of the project. Additionally, attention should be paid on the distinction between design work and the implementation of construction. During the implementation of construction works, we are more capable of detecting errors faster at the initial stage than at the stage of performing measurements, which suggests the need to focus on minimizing the occurrence of risk factors at the initial stage. Therefore, two questions have been asked. How to quantify the risk factors of geodetic works in road construction projects? How to allocate quantified risk factors of geodetic works in the schedule? The following article presents the description and the example of the practical use of the risk assessment procedure of geodetic works and risk allocation in the schedule based on the MORAG method (Method of Risk Analysis for Geodesy), which is the original method of risk analysis of geodetic works in road construction projects. As a result of these works, the risk values for the i-th risk factor and i-th geodetic task were determined, considering the increase in the duration of the work, the increase in the costs of the work, and all evaluation criteria. Then, the extension was described and calculated based on the data obtained from the actual implementation of the road construction project, the value, which in this case is 11.05 days, was entered into the modified schedule. The results of this study may help to better understand the scale of the impact of the correctness of the implementation of geodesy tasks on the implementation of construction tasks. Additionally, they may serve to increase the awareness of the scale of consequences of incorrectly performed measurement tasks (demolition is necessary) and greater attention on the cooperation between the entities implementing these activities.

Abstract: Road construction projects are characterized by multitasking and the influence of the correct implementation of one task on another. In the subject literature, we can encounter the analysis of risk factors throughout the project, and yet, we rarely find the distinction and characteristics of the impact of risk factors resulting from the implementation of planning and measurement tasks, the correctness and timeliness that have a huge impact on the performance of subsequent tasks, and the success of the project. Additionally, attention should be paid on the distinction between design work and the implementation of construction. During the implementation of construction works, we are more capable of detecting errors faster at the initial stage than at the stage of performing measurements, which suggests the need to focus on minimizing the occurrence of risk factors at the initial stage. Therefore, two questions have been asked. How to quantify the risk factors of geodetic works in road construction projects? How to allocate quantified risk factors of geodetic works in the schedule? The following article presents the description and the example of the practical use of the risk assessment procedure of geodetic works and risk allocation in the schedule based on the MORAG method (Method of Risk Analysis for Geodesy), which is the original method of risk analysis of geodetic works in road construction projects. As a result of these works, the risk values for the i-th risk factor and i-th geodetic task were determined, considering the increase in the duration of the work, the increase in the costs of the work, and all evaluation criteria. Then, the extension was described and calculated based on the data obtained from the actual implementation of the road construction project, the value, which in this case is 11.05 days, was entered into the modified schedule. The results of this study may help to better understand the scale of the impact of the correctness of the implementation of geodesy tasks on the implementation of construction tasks. Additionally, they may serve to increase the awareness of the scale of consequences of incorrectly performed measurement tasks (demolition is necessary) and greater attention on the cooperation between the entities implementing these activities.
Keywords: risk analysis, surveying works, construction schedules, risk factors, engineering of construction projects

Introduction
A road construction project is a complex process consisting of various activities [1], which have a significant impact on the occurrence of many risk factors. These factors cause both delays and changes in the costs incurred.
The separation of elements threatening the proper implementation of constructed projects is the subject of articles on risk analysis processes [2][3][4]. The use of various methods and approaches to the risk analysis of road construction projects can be observed in the literature; yet, there are rarely any studies concerning risks in the area of geodetic works [5][6][7][8][9][10]. This fact determined the need to research in this field [11][12][13]. Therefore, a method of risk analysis of surveying works was developed [14]. The method is presented in Figure 1.
This method will increase the effectiveness of planning processes and should also increase the possibility of meeting the implementation deadlines, both for individual operations and for entire projects.
First, the risk assessment of geodetic works is presented. Then, the topic of the allocation of risk factors in geodetic tasks is undertaken, characterizing the manner of allocating the risk factors and the results. Section 3 describes the allocation of risks in the schedule with the description and the example of practical use. The work is concluded with a short summary.

Risk assessment of surveying works
In this work [14], the risk r i of the occurrence of the i-th geodetic disturbance was identified using expression (1), i.e., as a product of the probability p i of this disturbance occurrence and the consequences of its occurrence divided by the sum of these products for all n analyzed risk factors R i for disruptions to geodetic works: assuming that p i is the value of probability and the consequence c i is a number in the range from 0 to 1.
In ref. [14], calculations were made for 20 risk factors for surveying works, which were specified based on the literature review, experience, expert knowledge, available documentation, and case study analysis. These factors have been listed in refs [11][12][13][14]. Table 1 displays the risk factors together with specific risk values that may accompany their occurrence, where risk value r i t for the i-th risk factor, considering the increase in the duration of works, risk value r i c for the i-th risk factor, considering the cost increase of the work, risk value r i for the i-th risk factor considering all assessment criteria.
3 Allocation of risk factors in surveying tasks

The method for allocation of risk factors
The analyses assumed that the risk r i value for a given R i factor was determined simultaneously for the entire construction project. Table 2 displays a scheme of the matrix for the allocation of risk R i factors for specific surveying tasks G i . Hence, the value of the risk assigned to a given geodetic task g i can be determined from the dependence and if for a given surveying task G i no risk R factor occurs, i the risk value r i = 0.
As in the case of the size of risk r i of individual risk R i factors, the risk g i of individual surveying tasks G i can also be identified with only one of the selected criteria, i.e., time or cost, considered.
For this reason, the following designations were adopted in the paper: g ithe risk value for the i-th surveying task taking account of all assessment criteria, g i tthe risk value for the i-th geodetic task considering the extension of the duration of works, g i cthe risk value for the i-th geodetic task regarding the increase in the costs of these works.  (3), due to which the risk values g i t , g i c , and g i were obtained, respectively.

Method of risk allocation in the schedule
The method for the allocation of disruptions to schedules is presented below. The analyses assumed that the risk r i value for the factor R i was determined simultaneously for the entire construction project. If there is no risk R i factor for the geodetic task G i , the risk value v = 0. Table 4 displays the matrix for the allocation of risk R i factors for individual geodetic tasks G i . It was assumed in the analyses that the risk value for the i-th geodetic task regarding the extended duration of works g i t was calculated from formula (4): where p i is the probability of the risk R i factor occurrence and c i t is a consequence of the risk R i factor occurrence Determination and measurement of the geodetic control network Drainage of the road structure by performing culverts, stormwater drainage, sanitary sewer system or cleaning devices by means of delineation, installation of benchmarks as well as control measurements and preparation of documentation Finishing works: strengthening of escarpments, roadsides, ditches, gabions, and sewage Determination of the axes of designed devices, control measurement, and the preparation of as-built dimensional documentation according to the technical specification of traffic safety devices Staking prefabricated and monolithic elements of road greenery or reconstruction of tracks Staking and inventory of other cubature objects such as sheds, arbors, and bus bays The symbol x denotes the allocation of risk factors concerning the higher duration of the construction project.
Then, assume that the surveying error is detected in the first few construction activities B i following the surveying task and that there is a direct causal link between them and the surveying task in question.
The allocation of the risk factor takes place by extending the duration of the surveying task and the duration of construction tasks directly related to the discussed surveying task. The pattern has been created, as a result of these analyses: where W i is the extension, T i G the duration of the geodetic task, T k B the duration of the construction task, G i the geodetic task, g i t the risk value for the i-th geodetic task, n the number of risk R j factors, m the number of construction tasks B completed until a wrongly performed surveying task B is detected, γ a coefficient regarding the time of both the re-performance of the construction task T i B and the time of its demolition, with 1.0 ≤ γ.

Exemplary risk allocation in a schedule
In order to illustrate the risk allocation in the schedule, a fragment of the actual road construction schedule was used, as shown in Figure 5.
In this case, the geodetic task G 1 is to "retrace the route and mark elevation points". The analyses assumed that an error in the performance of this surveying task could be detected after the first construction activity following it, namely "humus layer removal" (B 1 ).  According to the presented schedule, the geodetic task duration T G 1 = 4 days, while the construction task duration T G 1 = 3 days. Following Figure 1, it was assumed that the risk value taking into account the increase in the duration of works g t 1 is 0.801 for the geodetic task G 2 , i.e., "retrace the route and mark elevation points". The task Z 1 was treated as equivalent to the geodetic task "staking construction objects in the field". The values of the coefficient γ considering the time of both the re-performance of the construction task T i B and the time of its demolition γ 1 = 1.6 (for the construction task "humus layer removal") were taken for calculations.
Thus, the extension W 1 of the whole construction project related to incorrectly performed geodetic task G 1 is 7.05 days, as The calculations made indicate that the duration of the corrected schedule regarding the possibility of a wrongly performed surveying task Z 1 should be assumed as T G 1 = 4 + 7.05 = 11.05 days.

Summary and conclusions
The presented results are the effect of using the acquired data and do not constitute unambiguous information, but a visualization of the method and an indication of its development directions. A failure to perform the surveying activity or its incorrect execution may lead to substantial financial losses, the extension of the project duration to an unacceptable level, or a failure to meet   Figure 5: The risk value for the i-th surveying task considering all criteria.
the quality standards. As can be easily seen, the necessity to perform this type of analysis, broaden the knowledge, even about the elements which at first glance are not essential, and pay attention to elementary activities are even necessary to limit the risk and failures. The advantages of the presented method are largely its simplicity, transparent procedure, targeting specific risk factors, and the possibility of its practical use.
The disadvantage of this method is the necessity to collect a large database on the basis of which the risk value is determined and further analysis is performed.
The limitations related to the conducted research are related to the long period of data collection due to the limited number of projects of this type.
The application of this method is characterized by the need to build an expert database of risk factors. Nevertheless, the presented method enables the determination of the impact of the identified risk factors on the time of schedule implementation, and thus, to determine the impact of these factors on the improvement of construction tasks. In the next stage, the expansion of the database is planned, which will increase the accuracy of the research.
This work constitutes a further step to understanding how to construct an optimal schedule that can enhance the capability to verify and reduce the impact of risk factors on the time and cost of the construction project when developing and building up the database. As technology and new technologies evolve, it should be borne in mind that it is impossible to create ideal solutions in a changing environment. On the other hand, it is feasible to use the knowledge and try, as in the case of the method presented in this paper, to create an expert system that, based on a teaching sequence of correctly identified objects, will support the decision-making process.
Conflict of interest: Authors state no conflict of interest.